Don't reschedule on RequestedVRamTooHigh errors

The libvirt driver validates the hw_video_ram image property,
if specified, and the flavor extra spec "hw_video:ram_max_mb"
is set. If validation fails, the libvirt driver raises
RequestedVRamTooHigh which is not handled explicitly in
ComputeManager._build_and_run_instance so it will result in
a RescheduledException to another compute to retry the spawn
but that will always fail because this isn't something that
is per-compute host.

This change adds the error handling in _build_and_run_instance
so that we'll fail and abort the build and not reschedule.

Long-term, this validation should be moved into the API code
since it's not specific to a compute host and would be user
error that should result in a 400 response.

Change-Id: I93b409ca2b7b36400759ee9d2cd5b71c6df186ab
Partial-Bug: #1770726

nova/compute/manager.py

@@ -2083,7 +2083,10 @@ class ComputeManager(manager.Manager):
                 exception.InvalidDiskFormat,
                 cursive_exception.SignatureVerificationError,
                 exception.VolumeEncryptionNotSupported,
-                exception.InvalidInput) as e:
+                exception.InvalidInput,
+                # TODO(mriedem): We should be validating RequestedVRamTooHigh
+                # in the API during server create and rebuild.
+                exception.RequestedVRamTooHigh) as e:
             self._notify_about_instance_usage(context, instance,
                     'create.error', fault=e)
             compute_utils.notify_about_instance_create(

nova/tests/unit/compute/test_compute_mgr.py

@@ -5466,6 +5466,10 @@ class ComputeManagerBuildInstanceTestCase(test.NoDBTestCase):
         self._test_build_and_run_spawn_exceptions(
             exception.InvalidInput(reason=""))
 
+    def test_build_and_run_requested_vram_too_high(self):
+        self._test_build_and_run_spawn_exceptions(
+            exception.RequestedVRamTooHigh(req_vram=200, max_vram=100))
+
     def _test_build_and_run_spawn_exceptions(self, exc):
         with test.nested(
                 mock.patch.object(self.compute.driver, 'spawn',