Add (and fix) flake8 checks in tox

Add config in tox to run flake8 checks. For now, only "F*" errors are
checked (errors reported by pyflakes). pep8 style checks are ignored for
now.

This is accompanied by changes in the code that are necessary to silence
these errors. Most of them were about unused imports, but also unsed
referenced and even undefined ones (meaning that this code path was
broken, gotta increase test coverage).

This setup will replace pylint which reports way too many errors to be
usable (see next commit).

2 files changed, 9 insertions, 4 deletions

diff --git a/pym/gentoolkit/eshowkw/keywords_content.py b/pym/gentoolkit/eshowkw/keywords_content.py
index 18926b4..786e8b9 100644
--- a/pym/gentoolkit/eshowkw/keywords_content.py
+++ b/pym/gentoolkit/eshowkw/keywords_content.py
@@ -166,8 +166,6 @@ class keywords_content:
 		Sort packages queried based on version and slot
 		%% pn , repo, slot, eapi, keywords
 		"""
-		from operator import itemgetter
-
 		if len(package_content) > 1:
 			ver_map = {}
 			for cpv in package_content:
diff --git a/pym/gentoolkit/eshowkw/keywords_header.py b/pym/gentoolkit/eshowkw/keywords_header.py
index 6557f60..ab9117e 100644
--- a/pym/gentoolkit/eshowkw/keywords_header.py
+++ b/pym/gentoolkit/eshowkw/keywords_header.py
@@ -2,6 +2,8 @@
 # Copyright 2001-2018 Gentoo Foundation
 # Distributed under the terms of the GNU General Public License v2
 
+from __future__ import print_function
+
 __all__ = ['keywords_header']
 
 import portage
@@ -9,12 +11,17 @@ import os
 import sys
 if sys.hexversion < 0x3000000:
 	from io import open
-from portage import _encodings, _unicode_decode, _unicode_encode
+from portage import _encodings, _unicode_encode
 from portage import settings as ports
-from portage.output import colorize
 from gentoolkit.eshowkw.display_pretty import colorize_string
 from gentoolkit.eshowkw.display_pretty import align_string
 
+# Copied from ekeyword
+def warning(msg):
+	"""Write |msg| as a warning to stderr"""
+	print('warning: %s' % msg, file=sys.stderr)
+
+
 # Copied from ekeyword, modified to support arch vs ~arch status
 def load_profile_data(portdir=None, repo='gentoo'):
 	"""Load the list of known arches from the tree