Refresh flake8 dependencies

Author: mdmintz

requirements.txt

@@ -124,7 +124,8 @@ pytest-cov==2.12.1;python_version<"3.6"
 pytest-cov==3.0.0;python_version>="3.6"
 flake8==3.7.9;python_version<"3.6"
 flake8==5.0.2;python_version>="3.6"
-mccabe==0.7.0
+mccabe==0.6.1;python_version<"3.6"
+mccabe==0.7.0;python_version>="3.6"
 pyflakes==2.1.1;python_version<"3.6"
 pyflakes==2.5.0;python_version>="3.6"
 pycodestyle==2.5.0;python_version<"3.6"

setup.py

@@ -254,7 +254,8 @@
         "flake": [
             'flake8==3.7.9;python_version<"3.6"',
             'flake8==5.0.2;python_version>="3.6"',
-            "mccabe==0.7.0",
+            'mccabe==0.6.1;python_version<"3.6"',
+            'mccabe==0.7.0;python_version>="3.6"',
             'pyflakes==2.1.1;python_version<"3.6"',
             'pyflakes==2.5.0;python_version>="3.6"',
             'pycodestyle==2.5.0;python_version<"3.6"',