Hello,

Apologies for the delay on replying - we appreciate your efforts and interest in improving this library!

We are aware that the time.clock() function has been removed, however in order to maintain support for older versions of Python, namely Python 2.7, we need to keep it in the library. The call is surrounded by a try-except clause, meaning that when running the code in a version which no longer supports time.clock(), time.process_time() is called instead.

Changing time.clock() to time.process_time() in these cases would make the code in both the try and except blocks identical:

try:
     # Python 2.7
     if self._requests_left is None or \
-         time.clock() > (self._last_response_received_time
+         time.process_time() > (self._last_response_received_time 
                       + _ALLOWANCE_STATE_REFRESH_SECONDS):
         self._get_usage()
except AttributeError:
      # Python 3.3+
      if self._requests_left is None or \
         time.process_time() > (self._last_response_received_time 
                                + _ALLOWANCE_STATE_REFRESH_SECONDS):
          self._get_usage()

Please let us know if there are any other issues with this! If not, this pull request will be closed.

And thank you again for your time!