.travis.yml: change python version to 3.9

Signed-off-by: Huang Rui <[email protected]>

Author: vowstar

.travis.yml

@@ -14,7 +14,7 @@ script:
   - python setup.py sdist
   - python setup.py bdist
   - if [ $(python -c 'import sys; print(".".join(map(str, sys.version_info[:2])))') == 2.7 ]; then twine check dist/* ; fi
-  - if [ $(python -c 'import sys; print(".".join(map(str, sys.version_info[:2])))') == 2.7 ]; then twine check dist/* ; fi
+  - if [ $(python -c 'import sys; print(".".join(map(str, sys.version_info[:2])))') == 3.9 ]; then twine check dist/* ; fi
 
 deploy:
   provider: pypi