code: def publish_post(self):
          
          payload = {'content': self.content_base64.decode('utf-8')}
  
          sha_blob = self.get_sha_blob()
          if sha_blob:
              commit_msg = 'ghPublish UPDATE: {}'.format(self.title)
              payload.update(sha=sha_blob)
              payload.update(message=commit_msg)
          else:
              commit_msg = 'ghPublish ADD: {}'.format(self.title)
              payload.update(message=commit_msg)
  
          r = requests.put(self.api_url,
                           auth=self.get_auth_details(),
                           data=json.dumps(payload))
          try:
              url = r.json()['content']['html_url']
              return r.status_code, url
          except KeyError:
              return r.status_code, None
docs: If it's a new file, add it.
          Else, update it.