Fix invalid call

bmspy/bms.py

@@ -171,7 +171,7 @@ def requestMessage(reqmsg):
             cleanup()
             return response
         except Exception as e:
-            print("error communicating...: {0}".function(str(e)))
+            print("error communicating...: {0}".format(str(e)))
     else:
         print("cannot open serial port")