Tests: Alembic, log entire command when `abcls` fails

This makes it easier to manually run the `abcls` when a test fails, aiding
inspection & fixing.

No function changes to actual Blender code.

tests/python/alembic_tests.py

@@ -76,7 +76,7 @@ class AbstractAlembicTest(AbstractBlenderRunnerTest):
         output = output.replace('\r\n', '\n').replace('\r', '\n')
 
         if proc.returncode:
-            raise AbcPropError('Error %d running abcls:\n%s' % (proc.returncode, output))
+            raise AbcPropError('Error %d running %s:\n%s' % (proc.returncode, ' '.join(command), output))
 
         # Mapping from value type to callable that can convert a string to Python values.
         converters = {