code: def _wait_for_travis_build(url, commit, committed_at):
      
      print('Waiting for a Travis build to appear '
            'for `%s` after `%s`...' % (commit, committed_at))
      import requests
  
      slug = _slug_from_url(url)
      start_time = time.time()
      build_id = None
  
      while time.time() - start_time < 60:
          with requests.get('https://api.travis-ci.org/repos/%s/builds' % slug,
                            headers=_travis_headers()) as r:
              if not r.ok:
                  raise RuntimeError('Could not reach the Travis API '
                                     'endpoint. Additional information: '
                                     '%s' % str(r.content))
  
              # Search through all commits and builds to find our build.
              commit_to_sha = {}
              json = r.json()
              for travis_commit in sorted(json['commits'],
                                          key=lambda x: x['committed_at']):
                  travis_committed_at = datetime.datetime.strptime(
                      travis_commit['committed_at'], '%Y-%m-%dT%H:%M:%SZ'
                  ).replace(tzinfo=utc)
                  if travis_committed_at < committed_at:
                      continue
                  commit_to_sha[travis_commit['id']] = travis_commit['sha']
  
              for build in json['builds']:
                  if (build['commit_id'] in commit_to_sha and
                          commit_to_sha[build['commit_id']] == commit):
  
                      build_id = build['id']
                      print('Travis build id: `%d`' % build_id)
                      print('Travis build URL: `https://travis-ci.org/'
                            '%s/builds/%d`' % (slug, build_id))
  
              if build_id is not None:
                  break
  
          time.sleep(3.0)
      else:
          raise RuntimeError('Timed out while waiting for a Travis build '
                             'to start. Is Travis configured for `%s`?' % url)
      return build_id
docs: Waits for a Travis build to appear with the given commit SHA