disable download tests for Travis CI (#2674)

.travis.yml

@@ -55,7 +55,7 @@ install:
     cd -
 
 script:
-  - pytest --cov-config .coveragerc --cov torchvision --cov $TV_INSTALL_PATH -k 'not TestVideoReader and not TestVideoTransforms and not TestIO' test
+  - pytest --cov-config .coveragerc --cov torchvision --cov $TV_INSTALL_PATH -k 'not TestVideoReader and not TestVideoTransforms and not TestIO' test --ignore=test/test_datasets_download.py
   - pytest test/test_hub.py
 
 after_success: