BUG: Strava Client is giving AttributeError while running the pytest running suite.

[marcelcaraciolo]

• [x ] I have checked that this issue has not already been reported.

• [ x] I have confirmed this bug exists on the latest version of runpandas.

• [x ] (optional) I have confirmed this bug exists on the master branch of runpandas.

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Problem description

Testing with new strava client is giving issues with variable not found.

` def refresh(self):

  if time.time() > self.token_expires_at:

E AttributeError: 'StravaClient' object has no attribute 'token_expires_at'

runpandas/io/strava/_client.py:101: AttributeError`

Expected Output

Testing passing.

runpandas version 0.5.1

[marcelcaraciolo]

Closed by #62