From Google Code, issue #221, reported by @mo. This is a more recent run post python3 merge below.
$ pyflakes html5lib/
html5lib/__init__.py:16: 'parse' imported but unused
html5lib/__init__.py:16: 'HTMLParser' imported but unused
html5lib/__init__.py:16: 'parseFragment' imported but unused
html5lib/__init__.py:17: 'getTreeBuilder' imported but unused
html5lib/__init__.py:18: 'getTreeWalker' imported but unused
html5lib/__init__.py:19: 'serialize' imported but unused
html5lib/inputstream.py:6: 'types' imported but unused
html5lib/inputstream.py:110: local variable 'data' is assigned to but never used
html5lib/inputstream.py:293: 'sys' imported but unused
html5lib/tokenizer.py:11: 'entitiesWindows1252' imported but unused
html5lib/tokenizer.py:12: 'asciiLowercase' imported but unused
html5lib/tokenizer.py:801: redefinition of unused 'scriptDataDoubleEscapedDashState' from line 778
html5lib/utils.py:3: 'version_info' imported but unused
html5lib/html5parser.py:4: 'sys' imported but unused
html5lib/html5parser.py:17: 'formattingElements' imported but unused
html5lib/html5parser.py:18: 'tableInsertModeElements' imported but unused
html5lib/html5parser.py:19: 'voidElements' imported but unused
html5lib/html5parser.py:20: redefinition of unused 'spaceCharacters' from line 16
html5lib/html5parser.py:91: local variable 'e' is assigned to but never used
html5lib/html5parser.py:408: local variable 'element' is assigned to but never used
html5lib/html5parser.py:1405: local variable 'name' is assigned to but never used
html5lib/html5parser.py:1591: local variable 'node' is assigned to but never used
html5lib/tests/__init__.py:12: 'support' imported but unused
html5lib/tests/test_serializer.py:18: 'html5parser' imported but unused
html5lib/tests/test_serializer.py:175: local variable 'test_name' is assigned to but never used
html5lib/tests/test_parser2.py:5: 'support' imported but unused
html5lib/tests/test_parser2.py:37: local variable 'doc' is assigned to but never used
html5lib/tests/support.py:15: 'html5lib' imported but unused
html5lib/tests/support.py:16: 'html5parser' imported but unused
html5lib/tests/support.py:46: 'lxml' imported but unused
html5lib/tests/test_sanitizer.py:3: 'os' imported but unused
html5lib/tests/test_sanitizer.py:4: 'sys' imported but unused
html5lib/tests/test_sanitizer.py:5: 'unittest' imported but unused
html5lib/tests/test_stream.py:3: 'support' imported but unused
html5lib/tests/tokenizertotree.py:10: 'test_parser' imported but unused
html5lib/tests/test_tokenizer.py:5: 'sys' imported but unused
html5lib/tests/test_tokenizer.py:7: 'io' imported but unused
html5lib/tests/test_tokenizer.py:183: local variable 'testName' is assigned to but never used
html5lib/tests/test_tokenizer.py:187: local variable 'skip' is assigned to but never used
html5lib/tests/test_parser.py:6: 'io' imported but unused
html5lib/tests/test_parser.py:14: 'html5lib' imported but unused
html5lib/tests/test_parser.py:15: 'treebuilders' imported but unused
html5lib/tests/test_treewalkers.py:16: 'LintError' imported but unused
html5lib/tests/test_treewalkers.py:16: 'LintFilter' imported but unused
html5lib/tests/test_treewalkers.py:20: redefinition of unused 'COMMENT' from line 109
html5lib/tests/test_treewalkers.py:87: 'ElementTree' imported but unused
html5lib/tests/test_encoding.py:3: 're' imported but unused
html5lib/tests/test_encoding.py:30: local variable 't' is assigned to but never used
html5lib/tests/test_encoding.py:47: local variable 'test_name' is assigned to but never used
html5lib/tests/test_encoding.py:55: 'chardet' imported but unused
html5lib/treebuilders/__init__.py:37: 'sys' imported but unused
html5lib/treebuilders/dom.py:5: 're' imported but unused
html5lib/treebuilders/dom.py:9: 'ihatexml' imported but unused
html5lib/treebuilders/etree.py:210: local variable 'finalText' is assigned to but never used
html5lib/treebuilders/etree.py:274: local variable 'finalText' is assigned to but never used
html5lib/trie/datrie.py:3: 'chain' imported but unused
html5lib/serializer/htmlserializer.py:27: redefinition of unused 'entities' from line 14
html5lib/serializer/htmlserializer.py:231: local variable 'attributes' is assigned to but never used
html5lib/treewalkers/dom.py:9: 'voidElements' imported but unused
html5lib/treewalkers/simpletree.py:50: undefined name '_node'
html5lib/treewalkers/lxmletree.py:8: 'sys' imported but unused
html5lib/treewalkers/lxmletree.py:13: 'voidElements' imported but unused
html5lib/treewalkers/_base.py:98: undefined name 'NodeImplementedError'
html5lib/treewalkers/_base.py:157: local variable 'endTag' is assigned to but never used
$ pyflakes html5lib/ | grep undefined
html5lib/treewalkers/simpletree.py:50: undefined name '_node'
html5lib/treewalkers/_base.py:98: undefined name 'NodeImplementedError'
html5lib/treewalkers/etree.py:129: undefined name 'moduleFactoryFactory'
From Google Code, issue #221, reported by @mo. This is a more recent run post python3 merge below.