Explicitly set pylint to call python3.7

Solve pylint passing error on annotations

.travis.yml

@@ -1,22 +1,22 @@
 dist: xenial
 language: python
 python:
- - 3.6
+ - 3.7
 
 cache:
  directories:
  - $HOME/.blender-cache
 
 before_install:
  - sudo apt-get update
- - sudo apt-get install --no-install-recommends -y libsdl1.2debian libglu1 python3-pip
- - sudo pip3 install --upgrade pip
- - sudo pip3 install --upgrade setuptools
- - sudo pip3 install -r requirements.txt
+ - pip install --upgrade pip
+ - pip install --upgrade setuptools
 
 install:
+ - sudo apt-get install --no-install-recommends -y libsdl1.2debian libglu1 python3-pip
+ - pip install -r requirements.txt
  - bash tests/install_blender.sh
  - source .envs
 
 script:
- - make all BLENDER=$BLENDER_BIN PYLINT=pylint PEP8=pycodestyle
+ - make all BLENDER=$BLENDER_BIN PYLINT='python3 -m pylint'

Makefile

@@ -1,5 +1,5 @@
 PYLINT = pylint
-PEP8 = pycodestyle 
+PEP8 = pycodestyle
 BLENDER = blender
 GODOT = godot