Only run prospector and mypy on Python 3.6 and 3.7

.travis.yml

@@ -17,20 +17,8 @@ matrix:
       env: DJANGO=master
     - python: 3.7
       env: DJANGO=master
-    - python: 3.8-dev
-      env: DJANGO=1.11
-    - python: 3.8-dev
-      env: DJANGO=2.1
-    - python: 3.8-dev
-      env: DJANGO=2.2
     - python: 3.8-dev
       env: DJANGO=master
-    - python: pypy3
-      env: DJANGO=1.11
-    - python: pypy3
-      env: DJANGO=2.1
-    - python: pypy3
-      env: DJANGO=2.2
     - python: pypy3
       env: DJANGO=master
   fast_finish: true

requirements.txt

@@ -1,7 +1,7 @@
 -e .
 coverage==4.5.4
-mypy==0.720
-prospector==1.1.6.2
+mypy==0.720                 ; python_version < '3.8' and python_implementation != 'PyPy'
+prospector==1.1.6.2         ; python_version < '3.8' and python_implementation != 'PyPy'
 pytest==5.1.1
 pytest-cov==2.7.1
 pytest-django==3.5.1

tox.ini

@@ -26,7 +26,7 @@ deps =
 usedevelop = True
 commands =
     pytest
-    prospector
-    mypy axes
+    {py36,py37}: prospector
+    {py36,py37}: mypy axes
 setenv =
     PYTHONDONTWRITEBYTECODE=1