Repurpose the installtion app for it's original intent which was let apps report on their dependencies and if they were met. This commit removes two more Python dependencies: GitPython and psutil.

mayan/apps/installation/classes.py

@@ -7,9 +7,10 @@ import sh
 
 try:
     pip = sh.Command('pip')
-    PIP = True
 except sh.CommandNotFound:
     PIP = False
+else:
+    PIP = True
 
 
 class PIPNotFound(Exception):