record SHA of conversion to black for git blame

ianhi · ianhi · commit 16c5c6eb4241 · 2020-09-04T22:56:02.000-04:00
see https://github.com/psf/black/tree/20.8b1#migrating-your-code-style-without-ruining-git-blame
diff --git a/.git-blame-ignore-revs b/.git-blame-ignore-revs
@@ -0,0 +1,2 @@
+# migrate code to black
+f922e2e1e60e3a964dbd07597e7c44c068b7ba1d
