pythonPackages.flake8-future-import: 0.4.5 -> 0.4.6 and fix build

The build is currently broken on master and 20.03. This upgrades to the latest
version and also disables the bad py2 test. I spent a long time trying to figure
out what the issue is, but since it's disabled upstream on python3 anyways let's
just skip it on python2 as well.

ZHF: #80379

pkgs/development/python-modules/flake8-future-import/default.nix

···
-{ lib, fetchFromGitHub, buildPythonPackage, fetchpatch, flake8, six }:
+{ lib, isPy27, fetchFromGitHub, buildPythonPackage, fetchpatch, flake8, six }:
 
 buildPythonPackage rec {
   pname = "flake8-future-import";
-  version = "0.4.5";
+  version = "0.4.6";
 
   # PyPI tarball doesn't include the test suite
   src = fetchFromGitHub {
     owner = "xZise";
     repo = "flake8-future-import";
     rev = version;
-    sha256 = "00fpxa6g8cabybnciwnpsbg60zhgydc966jgwyyggw1pcg0frdqr";
+    sha256 = "00q8n15xdnvqj454arn7xxksyrzh0dw996kjyy7g9rdk0rf8x82z";
   };
 
-  patches = [
-    # Add Python 3.7 support. Remove with the next release
-    (fetchpatch {
-      url = https://github.com/xZise/flake8-future-import/commit/cace194a44d3b95c9c1ed96640bae49183acca04.patch;
-      sha256 = "17pkqnh035j5s5c53afs8bk49bq7lnmdwqp5k7izx7sw80z73p9r";
-    })
-  ];
+  propagatedBuildInputs = [ flake8 six ];
 
-  propagatedBuildInputs = [ flake8 six ];
+  # Upstream disables this test case naturally on python 3, but it also fails
+  # inside NixPkgs for python 2. Since it's going to be deleted, we just skip it
+  # on py2 as well.
+  patches = lib.optionals isPy27 [ ./skip-test.patch ];
 
-  meta = {
-    homepage = https://github.com/xZise/flake8-future-import;
+  meta = with lib; {
     description = "A flake8 extension to check for the imported __future__ modules to make it easier to have a consistent code base";
-    license = lib.licenses.mit;
+    homepage = "https://github.com/xZise/flake8-future-import";
+    license = licenses.mit;
   };
 }

pkgs/development/python-modules/flake8-future-import/skip-test.patch

···
+diff --git a/test_flake8_future_import.py b/test_flake8_future_import.py
+index 84fde59..345f23f 100644
+--- a/test_flake8_future_import.py
++++ b/test_flake8_future_import.py
+@@ -230,7 +230,7 @@ class TestBadSyntax(TestCaseBase):
+     """Test using various bad syntax examples from Python's library."""
+ 
+ 
[e-mail](sys.version_info[:2] >= (3, 7), 'flake8 supports up to 3.6')
[e-mail]("Has issue with installed path for flake8 in python2")
+ class Flake8TestCase(TestCaseBase):
+ 
+     """