Skip check_egl_platform_ext in case of PermissionError

[bdrung]

pyopengl 3.1.9+dfsg-1.1 autopkgtest fails on arm64:

=================================== FAILURES ===================================
_________________________ test_check_egl_platform_ext __________________________

    @wraps(func)
    def test_x():
        log.info("Starting test: %s", filename)
        pipe = subprocess.Popen(
            [
                sys.executable,
                file,
            ],
            stdout=subprocess.PIPE,
            stderr=subprocess.PIPE,
        )
        try:
            stdout, stderr = pipe.communicate()
        except subprocess.TimeoutExpired:
            log.warning("TIMEOUT on %s", filename)
            pipe.kill()
            raise
        except subprocess.CalledProcessError as err:
            log.warning("ERROR reported by process: %s", err)
            raise
        output = stdout.decode('utf-8', errors='ignore')
        lines = [x.strip() for x in output.strip().splitlines()]
        if not lines:
            log.error(
                "Test did not produce output: %s",
                stderr.decode('utf-8', errors='ignore'),
            )
>           raise RuntimeError('Test script failure')
E           RuntimeError: Test script failure

tests/test_checks.py:77: RuntimeError
------------------------------ Captured log call -------------------------------
ERROR    test_checks:test_checks.py:73 Test did not produce output: Traceback (most recent call last):
  File "/tmp/autopkgtest.dCNMA4/autopkgtest_tmp/tests/check_egl_platform_ext.py", line 41, in <module>
    main()
    ~~~~^^
  File "/tmp/autopkgtest.dCNMA4/autopkgtest_tmp/tests/check_egl_platform_ext.py", line 21, in main
    with open(cards[0], "w") as f:
         ~~~~^^^^^^^^^^^^^^^
PermissionError: [Errno 13] Permission denied: '/dev/dri/renderD128'

Skip this test in case of a permission error on the DRI device.

Bug-Ubuntu: https://launchpad.net/bugs/2115791