.travis.yml: fix syntax error

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

Author: vowstar

.travis.yml

@@ -13,8 +13,8 @@ script:
   - pylint --enable=E --disable=W,R,C *.py
   - python setup.py sdist
   - python setup.py bdist
-  - [[ $(python -c 'import sys; print(".".join(map(str, sys.version_info[:2])))') == 2.7 ]] && twine check dist/*
-  - [[ $(python -c 'import sys; print(".".join(map(str, sys.version_info[:2])))') == 3.9 ]] && twine check dist/*
+  - 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
 
 deploy:
   provider: pypi