Update Python dependencies

Author: mdmintz

requirements.txt

@@ -41,8 +41,10 @@ coverage==5.1
 pyotp==2.3.0
 boto==2.49.0
 cffi==1.14.0
-flake8==3.8.1
-pyflakes==2.2.0
+flake8==3.7.9;python_version<"3.5"
+flake8==3.8.1;python_version>="3.5"
+pyflakes==2.1.1;python_version<"3.5"
+pyflakes==2.2.0;python_version>="3.5"
 certifi>=2020.4.5.1
 pdfminer.six==20191110;python_version<"3.5"
 pdfminer.six==20200402;python_version>="3.5"

setup.py

@@ -125,8 +125,10 @@
         'pyotp==2.3.0',
         'boto==2.49.0',
         'cffi==1.14.0',
-        'flake8==3.8.1',
-        'pyflakes==2.2.0',
+        'flake8==3.7.9;python_version<"3.5"',
+        'flake8==3.8.1;python_version>="3.5"',
+        'pyflakes==2.1.1;python_version<"3.5"',
+        'pyflakes==2.2.0;python_version>="3.5"',
         'certifi>=2020.4.5.1',
         'pdfminer.six==20191110;python_version<"3.5"',
         'pdfminer.six==20200402;python_version>="3.5"',