Simplified get_prog to not trigger any exception.

pip/util.py

@@ -26,11 +26,11 @@ __all__ = ['rmtree', 'display_path', 'backup_dir',
 
 
 def get_prog():
-    if hasattr(sys, 'argv') and sys.argv and os.path.basename(sys.argv[0]) in ('__main__.py', '-c'):
-        return "%s -m pip" % sys.executable
     try:
-        return sys.argv[0]
-    except (TypeError, IndexError):
+        if os.path.basename(sys.argv[0]) in ('__main__.py', '-c'):
+            return "%s -m pip" % sys.executable
+    except (AttributeError, TypeError, IndexError):
+        pass
     return 'pip'