tests: use raw strings in the test strings

Related-to: git-cola#823
Signed-off-by: David Aguilar <[email protected]>

Author: davvid

test/diffparse_test.py

@@ -30,8 +30,9 @@ def test_diff(self):
         self.assertEqual(hunks[0].lines[4], '+class DiffSource(object):\n')
         self.assertEqual(
                 hunks[0].lines[-1],
-                "         self._header_start_re = re.compile('^@@ -(\\d+)"
-                " \\+(\\d+),(\\d+) @@.*')\n")
+                r"         self._header_start_re = re.compile('^@@ -(\d+)"
+                r" \+(\d+),(\d+) @@.*')"
+                '\n')
 
         self.assertEqual(hunks[1].first_line_idx, 23)
         self.assertEqual(len(hunks[1].lines), 18)