[Tests] Replace isort test with flake8-isort

* Move the known_third_party back to setup.cfg with comments.

.travis.yml

@@ -25,7 +25,6 @@ env:
     - TOX_ENV=pydef
     - TOX_ENV=flake8
 #    - TOX_ENV=flake8-complexity
-    - TOX_ENV=isort
     - TOX_ENV=docs
 #    - TOX_ENV=todo
     - TOX_ENV=trial              APTPACKAGES="$APTPACKAGES $APTPACKAGES_GTKUI"

setup.cfg

@@ -16,8 +16,11 @@ frameworks = CoreFoundation, Foundation, AppKit
 
 [isort]
 known_standard_library = future_builtins
-# Ignore Windows specific modules
-known_third_party = bbfreeze, win32verstamp
+known_third_party =
+# Ignore Windows specific modules.
+    bbfreeze, win32verstamp,
+# Ignore gtk modules, primarily for tox testing.
+    pygtk, gtk, gobject, gtk.gdk, pango, cairo, pangocairo
 known_first_party = msgfmt, deluge
 order_by_type = true
 line_length = 120

tox.ini

@@ -13,7 +13,7 @@ max-line-length = 120
 ignore = E301,E309
 
 [tox]
-envlist = py27, flake8, isort, docs, pylint
+envlist = py27, flake8, docs, pylint
 minversion=1.8
 
 [testenv]
@@ -88,21 +88,6 @@ commands = {[testenv:pydef]commands}
 # Code style verification
 ###########################
 
-[testenv:isort]
-deps =
-    {[testenv]deps}
-    isort>=4.2.5
-whitelist_externals =
-    {[testenv]whitelist_externals}
-    isort
-commands =
-    isort --version
-    python -c "import subprocess, sys; output = subprocess.check_output(\
-        'isort -q --diff --recursive deluge docs packaging *.py\
-        -o pygtk -o gtk -o gobject -o gtk.gdk -o pango -o cairo -o pangocairo\
-        ', shell=True);\
-        print output; sys.exit(bool(output))"
-
 [testenv:flake8]
 # Disble site packages to avoid using system flake8 which uses hardcoded python path which imports the wrong libraries.
 sitepackages = False
@@ -110,9 +95,11 @@ deps =
     {[testenv]deps}
     flake8
     flake8-quotes
+    flake8-isort
     pep8-naming
 commands =
     flake8 --version
+    python -c 'import isort; print(isort.__version__)'
     flake8
 
 [testenv:flake8-complexity]