Revert "flake8: 2.5.4 -> 3.0.4"

This reverts commit 7026cdf9e9.
This reverts commit 0675eb1b5d.
This reverts commit 3c88d3a9c4.

---

flake8 versions 2 and 3 are api incompatible and this update breaks
stuff. Version 3 should be added as a seperate expression and compatible
packages should use it explicitly.

pkgs/development/python-modules/flake8/move-pytest-config-to-pytest-ini.patch

@@ -1,22 +0,0 @@
-diff -r ad8325924f04 pytest.ini
---- /dev/null	Thu Jan 01 00:00:00 1970 +0000
-+++ b/pytest.ini	Fri Sep 30 12:28:39 2016 +0200
-@@ -0,0 +1,4 @@
-+[pytest]
-+-norecursedirs = .git .* *.egg* old docs dist build
-+-addopts = -rwv
-+
-diff -r ad8325924f04 setup.cfg
---- a/setup.cfg	Fri Sep 30 09:22:39 2016 +0200
-+++ b/setup.cfg	Fri Sep 30 12:28:39 2016 +0200
-@@ -12,10 +12,6 @@
- 	pycodestyle >= 2.0.0, < 2.1.0
- 	mccabe >= 0.5.0, < 0.6.0
- 
--[pytest]
--norecursedirs = .git .* *.egg* old docs dist build
--addopts = -rw
--
- [egg_info]
- tag_build = 
- tag_date = 0

pkgs/top-level/python-packages.nix

@@ -10539,24 +10539,15 @@ in modules // {
 
   flake8 = buildPythonPackage rec {
     name = "flake8-${version}";
-    version = "3.0.4";
+    version = "2.5.4";
 
     src = pkgs.fetchurl {
       url = "mirror://pypi/f/flake8/${name}.tar.gz";
-      sha256 = "03cpdrjxh0fyi2qpdxbbrmxw7whiq3xr3p958gr6yzghk34i1hml";
+      sha256 = "0bs9cz4fr99r2rwig1b8jwaadl1nan7kgpdzqwj0bwbckwbmh7nc";
     };
 
-    buildInputs = with self; [ nose mock pytestrunner pytest ];
-    propagatedBuildInputs = with self; [ pyflakes pep8 mccabe enum34 configparser pycodestyle ];
-
-    patches = [
-      ../development/python-modules/flake8/move-pytest-config-to-pytest-ini.patch
-    ];
-
-    # Tests fail due to missing ini file.
-    preCheck = ''
-      touch tox.ini
-    '';
+    buildInputs = with self; [ nose mock ];
+    propagatedBuildInputs = with self; [ pyflakes pep8 mccabe ];
 
     meta = {
       description = "Code checking using pep8 and pyflakes";