Remove use of the uu standard library module

which is being removed in Python 3.13, by backporting
python/cpython@407c3af

Partial fix for #640 .

Also:
- Backport small fixes from upstream `email` library module
- Remove unused imports

Author: nsoranzo

src/future/backports/email/message.py

@@ -5,28 +5,27 @@
 
 """Basic message object for the email package object model."""
 from __future__ import absolute_import, division, unicode_literals
-from future.builtins import list, range, str, zip
 
 __all__ = ['Message']
 
-import re
-import uu
-import base64
 import binascii
-from io import BytesIO, StringIO
+import quopri
+import re
+from io import StringIO
 
 # Intrapackage imports
-from future.utils import as_native_str
+from future.builtins import list, range, str, zip
 from future.backports.email import utils
 from future.backports.email import errors
-from future.backports.email._policybase import compat32
 from future.backports.email import charset as _charset
 from future.backports.email._encoded_words import decode_b
-Charset = _charset.Charset
+from future.backports.email._policybase import compat32
+from future.utils import as_native_str
 
+Charset = _charset.Charset
 SEMISPACE = '; '
 
-# Regular expression that matches `special' characters in parameters, the
+# Regular expression that matches 'special' characters in parameters, the
 # existence of which force quoting of the parameter value.
 tspecials = re.compile(r'[ \(\)<>@,;:\\"/\[\]\?=]')
 
@@ -41,6 +40,7 @@ def _splitparam(param):
         return a.strip(), None
     return a.strip(), b.strip()
 
+
 def _formatparam(param, value=None, quote=True):
     """Convenience function to format and return a key=value pair.
 
@@ -75,6 +75,7 @@ def _formatparam(param, value=None, quote=True):
     else:
         return param
 
+
 def _parseparam(s):
     # RDM This might be a Header, so for now stringify it.
     s = ';' + str(s)
@@ -106,6 +107,37 @@ def _unquotevalue(value):
         return utils.unquote(value)
 
 
+def _decode_uu(encoded):
+    """Decode uuencoded data."""
+    decoded_lines = []
+    encoded_lines_iter = iter(encoded.splitlines())
+    for line in encoded_lines_iter:
+        if line.startswith(b"begin "):
+            mode, _, path = line.removeprefix(b"begin ").partition(b" ")
+            try:
+                int(mode, base=8)
+            except ValueError:
+                continue
+            else:
+                break
+    else:
+        raise ValueError("`begin` line not found")
+    for line in encoded_lines_iter:
+        if not line:
+            raise ValueError("Truncated input")
+        elif line.strip(b' \t\r\n\f') == b'end':
+            break
+        try:
+            decoded_line = binascii.a2b_uu(line)
+        except binascii.Error:
+            # Workaround for broken uuencoders by /Fredrik Lundh
+            nbytes = (((line[0]-32) & 63) * 4 + 5) // 3
+            decoded_line = binascii.a2b_uu(line[:nbytes])
+        decoded_lines.append(decoded_line)
+
+    return b''.join(decoded_lines)
+
+
 class Message(object):
     """Basic message object.
 
@@ -115,7 +147,7 @@ class Message(object):
     multipart or a message/rfc822), then the payload is a list of Message
     objects, otherwise it is a string.
 
-    Message objects implement part of the `mapping' interface, which assumes
+    Message objects implement part of the 'mapping' interface, which assumes
     there is exactly one occurrence of the header per message.  Some headers
     do in fact appear multiple times (e.g. Received) and for those headers,
     you must use the explicit API to set or get all the headers.  Not all of
@@ -181,7 +213,11 @@ def attach(self, payload):
         if self._payload is None:
             self._payload = [payload]
         else:
-            self._payload.append(payload)
+            try:
+                self._payload.append(payload)
+            except AttributeError:
+                raise TypeError("Attach is not valid on a message with a"
+                                " non-multipart payload")
 
     def get_payload(self, i=None, decode=False):
         """Return a reference to the payload.
@@ -238,22 +274,22 @@ def get_payload(self, i=None, decode=False):
                 bpayload = payload.encode('ascii', 'surrogateescape')
                 if not decode:
                     try:
-                        payload = bpayload.decode(self.get_param('charset', 'ascii'), 'replace')
+                        payload = bpayload.decode(self.get_content_charset('ascii'), 'replace')
                     except LookupError:
                         payload = bpayload.decode('ascii', 'replace')
             elif decode:
                 try:
                     bpayload = payload.encode('ascii')
                 except UnicodeError:
                     # This won't happen for RFC compliant messages (messages
-                    # containing only ASCII codepoints in the unicode input).
+                    # containing only ASCII code points in the unicode input).
                     # If it does happen, turn the string into bytes in a way
                     # guaranteed not to fail.
                     bpayload = payload.encode('raw-unicode-escape')
         if not decode:
             return payload
         if cte == 'quoted-printable':
-            return utils._qdecode(bpayload)
+            return quopri.decodestring(bpayload)
         elif cte == 'base64':
             # XXX: this is a bit of a hack; decode_b should probably be factored
             # out somewhere, but I haven't figured out where yet.
@@ -262,13 +298,10 @@ def get_payload(self, i=None, decode=False):
                 self.policy.handle_defect(self, defect)
             return value
         elif cte in ('x-uuencode', 'uuencode', 'uue', 'x-uue'):
-            in_file = BytesIO(bpayload)
-            out_file = BytesIO()
             try:
-                uu.decode(in_file, out_file, quiet=True)
-                return out_file.getvalue()
-            except uu.Error:
-                # Some decoding problem
+                return _decode_uu(bpayload)
+            except ValueError:
+                # Some decoding problem.
                 return bpayload
         if isinstance(payload, str):
             return bpayload
@@ -355,7 +388,7 @@ def __setitem__(self, name, val):
         if max_count:
             lname = name.lower()
             found = 0
-            for k, v in self._headers:
+            for k, _ in self._headers:
                 if k.lower() == lname:
                     found += 1
                     if found >= max_count:
@@ -376,10 +409,14 @@ def __delitem__(self, name):
         self._headers = newheaders
 
     def __contains__(self, name):
-        return name.lower() in [k.lower() for k, v in self._headers]
+        name_lower = name.lower()
+        for k, _ in self._headers:
+            if name_lower == k.lower():
+                return True
+        return False
 
     def __iter__(self):
-        for field, value in self._headers:
+        for field, _ in self._headers:
             yield field
 
     def keys(self):
@@ -505,7 +542,7 @@ def replace_header(self, _name, _value):
         raised.
         """
         _name = _name.lower()
-        for i, (k, v) in zip(range(len(self._headers)), self._headers):
+        for i, (k, _) in zip(range(len(self._headers)), self._headers):
             if k.lower() == _name:
                 self._headers[i] = self.policy.header_store_parse(k, _value)
                 break
@@ -520,7 +557,7 @@ def get_content_type(self):
         """Return the message's content type.
 
         The returned string is coerced to lower case of the form
-        `maintype/subtype'.  If there was no Content-Type header in the
+        'maintype/subtype'.  If there was no Content-Type header in the
         message, the default type as given by get_default_type() will be
         returned.  Since according to RFC 2045, messages always have a default
         type this will always return a value.
@@ -543,7 +580,7 @@ def get_content_type(self):
     def get_content_maintype(self):
         """Return the message's main content type.
 
-        This is the `maintype' part of the string returned by
+        This is the 'maintype' part of the string returned by
         get_content_type().
         """
         ctype = self.get_content_type()
@@ -552,14 +589,14 @@ def get_content_maintype(self):
     def get_content_subtype(self):
         """Returns the message's sub-content type.
 
-        This is the `subtype' part of the string returned by
+        This is the 'subtype' part of the string returned by
         get_content_type().
         """
         ctype = self.get_content_type()
         return ctype.split('/')[1]
 
     def get_default_type(self):
-        """Return the `default' content type.
+        """Return the 'default' content type.
 
         Most messages have a default content type of text/plain, except for
         messages that are subparts of multipart/digest containers.  Such
@@ -568,7 +605,7 @@ def get_default_type(self):
         return self._default_type
 
     def set_default_type(self, ctype):
-        """Set the `default' content type.
+        """Set the 'default' content type.
 
         ctype should be either "text/plain" or "message/rfc822", although this
         is not enforced.  The default content type is not stored in the
@@ -601,8 +638,8 @@ def get_params(self, failobj=None, header='content-type', unquote=True):
         """Return the message's Content-Type parameters, as a list.
 
         The elements of the returned list are 2-tuples of key/value pairs, as
-        split on the `=' sign.  The left hand side of the `=' is the key,
-        while the right hand side is the value.  If there is no `=' sign in
+        split on the '=' sign.  The left hand side of the '=' is the key,
+        while the right hand side is the value.  If there is no '=' sign in
         the parameter the value is the empty string.  The value is as
         described in the get_param() method.
 
@@ -664,7 +701,7 @@ def set_param(self, param, value, header='Content-Type', requote=True,
         message, it will be set to "text/plain" and the new parameter and
         value will be appended as per RFC 2045.
 
-        An alternate header can specified in the header argument, and all
+        An alternate header can be specified in the header argument, and all
         parameters will be quoted as necessary unless requote is False.
 
         If charset is specified, the parameter will be encoded according to RFC
@@ -759,9 +796,9 @@ def get_filename(self, failobj=None):
         """Return the filename associated with the payload if present.
 
         The filename is extracted from the Content-Disposition header's
-        `filename' parameter, and it is unquoted.  If that header is missing
-        the `filename' parameter, this method falls back to looking for the
-        `name' parameter.
+        'filename' parameter, and it is unquoted.  If that header is missing
+        the 'filename' parameter, this method falls back to looking for the
+        'name' parameter.
         """
         missing = object()
         filename = self.get_param('filename', missing, 'content-disposition')
@@ -774,7 +811,7 @@ def get_filename(self, failobj=None):
     def get_boundary(self, failobj=None):
         """Return the boundary associated with the payload if present.
 
-        The boundary is extracted from the Content-Type header's `boundary'
+        The boundary is extracted from the Content-Type header's 'boundary'
         parameter, and it is unquoted.
         """
         missing = object()

src/future/backports/email/utils.py

@@ -33,24 +33,18 @@
 if utils.PY2:
     re.ASCII = 0
 import time
-import base64
 import random
 import socket
 from future.backports import datetime
 from future.backports.urllib.parse import quote as url_quote, unquote as url_unquote
-import warnings
-from io import StringIO
 
 from future.backports.email._parseaddr import quote
 from future.backports.email._parseaddr import AddressList as _AddressList
 from future.backports.email._parseaddr import mktime_tz
 
 from future.backports.email._parseaddr import parsedate, parsedate_tz, _parsedate_tz
 
-from quopri import decodestring as _qdecode
-
 # Intrapackage imports
-from future.backports.email.encoders import _bencode, _qencode
 from future.backports.email.charset import Charset
 
 COMMASPACE = ', '
@@ -67,6 +61,7 @@
 _has_surrogates = re.compile(
     '([^\ud800-\udbff]|\A)[\udc00-\udfff]([^\udc00-\udfff]|\Z)').search
 
+
 # How to deal with a string containing bytes before handing it to the
 # application through the 'normal' interface.
 def _sanitize(string):
@@ -85,13 +80,13 @@ def formataddr(pair, charset='utf-8'):
     If the first element of pair is false, then the second element is
     returned unmodified.
 
-    Optional charset if given is the character set that is used to encode
+    The optional charset is the character set that is used to encode
     realname in case realname is not ASCII safe.  Can be an instance of str or
     a Charset-like object which has a header_encode method.  Default is
     'utf-8'.
     """
     name, address = pair
-    # The address MUST (per RFC) be ascii, so raise an UnicodeError if it isn't.
+    # The address MUST (per RFC) be ascii, so raise a UnicodeError if it isn't.
     address.encode('ascii')
     if name:
         try:
@@ -110,15 +105,13 @@ def formataddr(pair, charset='utf-8'):
     return address
 
 
-
 def getaddresses(fieldvalues):
     """Return a list of (REALNAME, EMAIL) for each fieldvalue."""
     all = COMMASPACE.join(fieldvalues)
     a = _AddressList(all)
     return a.addresslist
 
 
-
 ecre = re.compile(r'''
   =\?                   # literal =?
   (?P<charset>[^?]*?)   # non-greedy up to the next ? is the charset
@@ -139,12 +132,13 @@ def _format_timetuple_and_zone(timetuple, zone):
         timetuple[0], timetuple[3], timetuple[4], timetuple[5],
         zone)
 
+
 def formatdate(timeval=None, localtime=False, usegmt=False):
     """Returns a date string as specified by RFC 2822, e.g.:
 
     Fri, 09 Nov 2001 01:08:47 -0000
 
-    Optional timeval if given is a floating point time value as accepted by
+    Optional timeval if given is a floating-point time value as accepted by
     gmtime() and localtime(), otherwise the current time is used.
 
     Optional localtime is a flag that when True, interprets timeval, and
@@ -184,6 +178,7 @@ def formatdate(timeval=None, localtime=False, usegmt=False):
             zone = '-0000'
     return _format_timetuple_and_zone(now, zone)
 
+
 def format_datetime(dt, usegmt=False):
     """Turn a datetime into a date string as specified in RFC 2822.
 
@@ -254,7 +249,6 @@ def unquote(str):
     return str
 
 
-
 # RFC2231-related functions - parameter encoding and decoding
 def decode_rfc2231(s):
     """Decode string according to RFC 2231"""
@@ -282,6 +276,7 @@ def encode_rfc2231(s, charset=None, language=None):
 rfc2231_continuation = re.compile(r'^(?P<name>\w+)\*((?P<num>[0-9]+)\*?)?$',
     re.ASCII)
 
+
 def decode_params(params):
     """Decode parameters list according to RFC 2231.
 
@@ -338,6 +333,7 @@ def decode_params(params):
                 new_params.append((name, '"%s"' % value))
     return new_params
 
+
 def collapse_rfc2231_value(value, errors='replace',
                            fallback_charset='us-ascii'):
     if not isinstance(value, tuple) or len(value) != 3: