Stop supporting running tests without Xvfb/DISPLAY

This always caused problems and unneeded complexity in the past, and it
also increases Travis CI runtime.

We now require either a DISPLAY during tests or Xvfb being installed.

.travis.yml

@@ -7,8 +7,6 @@ matrix:
   include:
     - os: linux
       env: TESTENV=py34-cov
-    - os: linux
-      env: TESTENV=unittests-nodisp
     - os: linux
       env: DOCKER=debian-jessie
       services: docker

tests/conftest.py

@@ -100,13 +100,6 @@ def pytest_collection_modifyitems(items):
     for item in items:
         if 'qapp' in getattr(item, 'fixturenames', ()):
             item.add_marker('gui')
-            if sys.platform == 'linux' and not os.environ.get('DISPLAY', ''):
-                if ('CI' in os.environ and
-                        not os.environ.get('QUTE_NO_DISPLAY', '')):
-                    raise Exception("No display available on CI!")
-                skip_marker = pytest.mark.skipif(
-                    True, reason="No DISPLAY available")
-                item.add_marker(skip_marker)
 
         if hasattr(item, 'module'):
             module_path = os.path.relpath(
@@ -151,12 +144,15 @@ def pytest_addoption(parser):
 
 
 @pytest.fixture(scope='session', autouse=True)
-def prevent_xvfb_on_buildbot(request):
+def check_display(request):
     if (not request.config.getoption('--no-xvfb') and
             'QUTE_BUILDBOT' in os.environ and
             request.config.xvfb is not None):
         raise Exception("Xvfb is running on buildbot!")
 
+    if sys.platform == 'linux' and not os.environ.get('DISPLAY', ''):
+        raise Exception("No display and no Xvfb available!")
+
 
 @pytest.hookimpl(tryfirst=True, hookwrapper=True)
 def pytest_runtest_makereport(item, call):

tox.ini

@@ -90,17 +90,6 @@ commands =
     {envpython} scripts/dev/freeze_tests.py build_exe -b {envdir}/build
     {envdir}/build/run-frozen-tests {posargs}
 
-[testenv:unittests-nodisp]
-basepython = python3
-passenv = {[testenv]passenv}
-deps = {[testenv]deps}
-setenv =
-    DISPLAY=
-    QUTE_NO_DISPLAY=1
-commands =
-    {envpython} scripts/link_pyqt.py --tox {envdir}
-    {envpython} -m pytest {posargs:tests}
-
 [testenv:misc]
 ignore_errors = true
 basepython = python3