Nicer error message when OpenAL is not installed.
Nicer error message when OpenAL is not installed.

kmonsoor/pyglet,kmonsoor/pyglet,mpasternak/michaldtz-fixes-518-522,odyaka341/pyglet,mpasternak/michaldtz-fix-552,Austin503/pyglet,kmonsoor/pyglet,qbektrix/pyglet,google-code-export/pyglet,qbektrix/pyglet,qbektrix/pyglet,odyaka341/pyglet,shaileshgoogler/pyglet,mpasternak/michaldtz-fix-552,Alwnikrotikz/pyglet,odyaka341/pyglet,mpasternak/pyglet-fix-issue-518-522,shaileshgoogler/pyglet,cledio66/pyglet,xshotD/pyglet,mpasternak/michaldtz-fix-552,xshotD/pyglet,arifgursel/pyglet,Austin503/pyglet,arifgursel/pyglet,mpasternak/pyglet-fix-issue-518-522,gdkar/pyglet,cledio66/pyglet,Austin503/pyglet,Alwnikrotikz/pyglet,mpasternak/pyglet-fix-issue-552,gdkar/pyglet,xshotD/pyglet,Austin503/pyglet,gdkar/pyglet,shaileshgoogler/pyglet,shaileshgoogler/pyglet,mpasternak/pyglet-fix-issue-518-522,Alwnikrotikz/pyglet,mpasternak/pyglet-fix-issue-552,mpasternak/pyglet-fix-issue-518-522,mpasternak/michaldtz-fixes-518-522,shaileshgoogler/pyglet,google-code-export/pyglet,cledio66/pyglet,qbektrix/pyglet,mpasternak/michaldtz-fix-552,cledio66/pyglet,google-code-export/pyglet,arifgursel/pyglet,odyaka341/pyglet,Alwnikrotikz/pyglet,gdkar/pyglet,qbektrix/pyglet,gdkar/pyglet,mpasternak/pyglet-fix-issue-552,mpasternak/michaldtz-fixes-518-522,arifgursel/pyglet,xshotD/pyglet,mpasternak/michaldtz-fixes-518-522,odyaka341/pyglet,xshotD/pyglet,mpasternak/pyglet-fix-issue-552,cledio66/pyglet,kmonsoor/pyglet,google-code-export/pyglet,kmonsoor/pyglet,arifgursel/pyglet,google-code-export/pyglet,Alwnikrotikz/pyglet,Austin503/pyglet