tests: skip pvgrub tests on Fedora

Fedora compresses the kernel with zstd now, which isn't suppported in
grub (as of 2.04). Since we don't care about PV that much anymore,
simply skip the test there.

qubes/tests/integ/grub.py

@@ -157,6 +157,15 @@ class TC_40_PVGrub(GrubBase):
     virt_mode = 'pv'
     kernel = 'pvgrub2'
 
+    def setUp(self):
+        if 'fedora' in self.template:
+            # requires a zstd decompression filter in grub
+            # (see grub_file_filter_id enum in grub sources)
+            self.skipTest('Fedora kernel is compressed with zstd '
+                          'which is not supported by pvgrub2')
+        super().setUp()
+
+
 class TC_41_HVMGrub(GrubBase):
     virt_mode = 'hvm'
     kernel = None