tox: generic twisted factor

tox.ini

@@ -26,7 +26,7 @@ commands =
     coverage: coverage report
 passenv = USER USERNAME COVERAGE_* TRAVIS PYTEST_ADDOPTS
 setenv =
-    _PYTEST_TOX_DEFAULT_POSARGS={env:_PYTEST_TOX_POSARGS_LSOF:} {env:_PYTEST_TOX_POSARGS_PEXPECT:} {env:_PYTEST_TOX_POSARGS_XDIST:}
+    _PYTEST_TOX_DEFAULT_POSARGS={env:_PYTEST_TOX_POSARGS_LSOF:} {env:_PYTEST_TOX_POSARGS_PEXPECT:} {env:_PYTEST_TOX_POSARGS_TWISTED:} {env:_PYTEST_TOX_POSARGS_XDIST:}
 
     # Configuration to run with coverage similar to Travis/Appveyor, e.g.
     # "tox -e py37-coverage".
@@ -42,12 +42,16 @@ setenv =
     pexpect: _PYTEST_TOX_PLATFORM=linux|darwin
     pexpect: _PYTEST_TOX_POSARGS_PEXPECT=testing/test_pdb.py testing/test_terminal.py testing/test_unittest.py
 
+    twisted: _PYTEST_TOX_POSARGS_TWISTED=testing/test_unittest.py
+
     xdist: _PYTEST_TOX_POSARGS_XDIST=-n auto
 extras = testing
 deps =
     numpy: numpy
     pexpect: pexpect
     pluggymaster: git+https://github.com/pytest-dev/pluggy.git@master
+    twisted: twisted
+    twisted: unittest2
     xdist: pytest-xdist>=1.13
     {env:_PYTEST_TOX_EXTRA_DEP:}
 platform = {env:_PYTEST_TOX_PLATFORM:.*}
@@ -67,18 +71,6 @@ basepython = python3
 deps = pre-commit>=1.11.0
 commands = pre-commit run --all-files --show-diff-on-failure
 
-[testenv:py27-twisted]
-deps =
-    {[testenv]deps}
-    twisted
-    unittest2
-commands =
-    {env:_PYTEST_TOX_COVERAGE_RUN:} pytest {posargs:testing/test_unittest.py}
-
-[testenv:py37-twisted]
-deps = {[testenv:py27-twisted]deps}
-commands = {[testenv:py27-twisted]commands}
-
 [testenv:docs]
 basepython = python3
 skipsdist = True