Change comparison is to == to avoid SyntaxWarning (#388)

This fixes `SyntaxWarning: "is" with a literal. Did you mean "=="?`.

Signed-off-by: Thanh Phan <[email protected]>

getgauge/python.py

@@ -2,7 +2,7 @@
 import warnings
 from getgauge.registry import registry, MessagesStore, ScreenshotsStore
 
-if sys.version_info[0] is 3:
+if sys.version_info[0] == 3:
     from collections.abc import MutableMapping
 else:
     from collections import MutableMapping