Update Python dependencies

Author: mdmintz

requirements.txt

@@ -11,7 +11,8 @@ PyYAML>=5.4.1;python_version>="3.6"
 certifi>=2020.12.5
 six==1.15.0
 nose==1.3.7
-ipdb==0.13.5
+ipdb==0.13.4;python_version<"3.6"
+ipdb==0.13.5;python_version>="3.6"
 parso==0.7.1;python_version<"3.6"
 parso==0.8.1;python_version>="3.6"
 jedi==0.17.2;python_version<"3.6"

setup.py

@@ -115,7 +115,8 @@
         'certifi>=2020.12.5',
         'six==1.15.0',
         'nose==1.3.7',
-        'ipdb==0.13.5',
+        'ipdb==0.13.4;python_version<"3.6"',
+        'ipdb==0.13.5;python_version>="3.6"',
         'parso==0.7.1;python_version<"3.6"',
         'parso==0.8.1;python_version>="3.6"',
         'jedi==0.17.2;python_version<"3.6"',