Implement interpreter test on travis

.travis.yml

@@ -15,6 +15,7 @@ env:
   - JEDI_TEST_ENVIRONMENT=36
   - JEDI_TEST_ENVIRONMENT=37
   - JEDI_TEST_ENVIRONMENT=38
+  - JEDI_TEST_ENVIRONMENT=interpreter
 
 matrix:
   include:

conftest.py

@@ -90,13 +90,13 @@ def clean_jedi_cache(request):
 
 @pytest.fixture(scope='session')
 def environment(request):
-    if request.config.option.interpreter_env:
-        return InterpreterEnvironment()
-
     version = request.config.option.env
     if version is None:
         version = os.environ.get('JEDI_TEST_ENVIRONMENT', str(py_version))
 
+    if request.config.option.interpreter_env or version == 'interpreter':
+        return InterpreterEnvironment()
+
     return get_system_environment(version[0] + '.' + version[1:])
 
 

tox.ini

@@ -27,6 +27,7 @@ setenv =
     env35: JEDI_TEST_ENVIRONMENT=35
     env36: JEDI_TEST_ENVIRONMENT=36
     env37: JEDI_TEST_ENVIRONMENT=37
+    interpreter: JEDI_TEST_ENVIRONMENT=interpreter
 commands =
     pytest {posargs}
 [testenv:cov-py37]