Update .gitlab-ci.yml

Revert python3.5 to python3, because python3.5 is not installed

.gitlab-ci.yml

@@ -3,7 +3,7 @@
 image: python:latest
 
 before_script:
-  - python3.5 -V                                   # Print out python version for debugging
+  - python3 -V                                   # Print out python version for debugging
 
 stages:
   - build
@@ -11,7 +11,7 @@ stages:
 
 build:
   script:
-  - python3.5 setup.py bdist_wheel
+  - python3 setup.py bdist_wheel
   # an alternative approach is to install and run:
   # - pip3 install dist/*
   # run the command here
@@ -21,7 +21,7 @@ build:
 
 test:
   script:
-  - python3.5 setup.py test
+  - python3 setup.py test
   - pip3 install tox flake8  # you can also use tox
   - tox -e py36,flake8