Make isort compatible with black

isort's lines_after_imports = 2 conflicted with black, so run-cleanup
reverted black's changes. Use isort's black profile instead and apply the
resulting formatting. Also fix the flake8 errors in check_email_mixin and
drop a leftover debug print.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

setup.cfg

@@ -2,12 +2,7 @@
 max_line_length = 96
 
 [isort]
-include_trailing_comma = true
-multi_line_output = 3
-lines_after_imports = 2
+profile = black
 combine_as_imports = true
-force_grid_wrap = 0
-use_parentheses = true
-line_length = 88
 known_first_party = max
 known_third_party = flask