Improve version.opengl_vendor()

On Windows with OpenGL ES we can't use versionFunctions, so we just return None
early.

Also, this fixes some lint and adds a smoke test.

qutebrowser/utils/version.py

@@ -380,12 +380,15 @@ def version():
 
 
 def opengl_vendor():  # pragma: no cover
-    """Get the OpenGL vendor used."""
+    """Get the OpenGL vendor used.
+
+    This returns a string such as 'nouveau' or
+    'Intel Open Source Technology Center'; or None if the vendor can't be
+    determined.
+    """
     # We're doing those imports here because this is only available with Qt 5.4
     # or newer.
-    from PyQt5.QtWidgets import QOpenGLWidget
-    from PyQt5.QtOpenGL import QGLWidget
-    from PyQt5.QtGui import QOpenGLContext, QSurfaceFormat, QOpenGLVersionProfile, QOffscreenSurface
+    from PyQt5.QtGui import QOpenGLContext, QOpenGLVersionProfile, QOffscreenSurface
     assert QApplication.instance()
     assert QOpenGLContext.currentContext() is None
 
@@ -393,6 +396,10 @@ def opengl_vendor():  # pragma: no cover
     surface.create()
 
     ctx = QOpenGLContext()
+    if ctx.isOpenGLES():
+        # Can't use versionFunctions there
+        return None
+
     ok = ctx.create()
     assert ok
 

tests/unit/utils/test_version.py

@@ -34,7 +34,7 @@ import pkg_resources
 import pytest
 
 import qutebrowser
-from qutebrowser.utils import version, usertypes
+from qutebrowser.utils import version, usertypes, qtutils
 from qutebrowser.browser import pdfjs
 
 
@@ -918,3 +918,10 @@ def test_version_output(git_commit, frozen, style, with_webkit,
 
     expected = template.rstrip('\n').format(**substitutions)
     assert version.version() == expected
+
+
+@pytest.mark.skipif(not qtutils.version_check('5.4'),
+                    reason="Needs Qt >= 5.4.")
+def test_opengl_vendor():
+    """Simply call version.opengl_vendor() and see if it doesn't crash."""
+    return version.opengl_vendor()