travis-ci force oauth2client==1.5.2 to fix android deploy

.travis.yml

@@ -124,7 +124,8 @@ script:
 
 after_success:
   - if [[ "${TRAVIS_OS_NAME}" = "android" && "${TRAVIS_PULL_REQUEST}" = "false" && "${TRAVIS_BRANCH}" = "master" ]]; then
-         pip install --user google-api-python-client PyOpenSSL
+         pip install --user oauth2client==1.5.2
+      && pip install --user google-api-python-client PyOpenSSL
       && cd ${SHADOW_BUILD_DIR} && openssl aes-256-cbc -K $encrypted_25db6eb7c3fd_key -iv $encrypted_25db6eb7c3fd_iv -in ${TRAVIS_BUILD_DIR}/Google_Play_Android_Developer-bb93ae7d61ca.p12.enc -out Google_Play_Android_Developer-bb93ae7d61ca.p12 -d
       && ${TRAVIS_BUILD_DIR}/tools/google_play_upload.py org.mavlink.qgroundcontrol ${SHADOW_BUILD_DIR}/release/package/qgroundcontrol.apk
       ;