Resolved problem in virtualenv detection

Fix #1535

bazarr/init.py

@@ -45,8 +45,10 @@ import logging
 
 def is_virtualenv():
     # return True if Bazarr have been start from within a virtualenv or venv
-    base_prefix = getattr(sys, "base_prefix", None) or getattr(sys, "real_prefix", None) or sys.prefix
-    return base_prefix != sys.prefix
+    base_prefix = getattr(sys, "base_prefix", None)
+    # real_prefix will return None if not in a virtualenv enviroment or the default python path
+    real_prefix = getattr(sys, "real_prefix", None) or sys.prefix
+    return base_prefix != real_prefix
 
 
 # deploy requirements.txt