perf: upgrade XBlock to 5.1.1 for caching unknown tags

This should improve performance for courseware operations when there is
content that doesn't map to any existing XBlocks in the system. This
usually happens to old courses when custom XBlock types are deprecated
and removed, or when a course is imported from another instance with a
different set of installed XBlocks.

requirements/edx/base.txt

@@ -1256,7 +1256,7 @@ wheel==0.45.1
     # via django-pipeline
 wrapt==1.17.2
     # via -r requirements/edx/kernel.in
-xblock[django]==5.1.0
+xblock[django]==5.1.1
     # via
     #   -r requirements/edx/kernel.in
     #   acid-xblock

requirements/edx/development.txt

@@ -2253,7 +2253,7 @@ wrapt==1.17.2
     #   -r requirements/edx/doc.txt
     #   -r requirements/edx/testing.txt
     #   astroid
-xblock[django]==5.1.0
+xblock[django]==5.1.1
     # via
     #   -r requirements/edx/doc.txt
     #   -r requirements/edx/testing.txt

requirements/edx/doc.txt

@@ -1583,7 +1583,7 @@ wrapt==1.17.2
     # via
     #   -r requirements/edx/base.txt
     #   astroid
-xblock[django]==5.1.0
+xblock[django]==5.1.1
     # via
     #   -r requirements/edx/base.txt
     #   acid-xblock

requirements/edx/testing.txt

@@ -1673,7 +1673,7 @@ wrapt==1.17.2
     # via
     #   -r requirements/edx/base.txt
     #   astroid
-xblock[django]==5.1.0
+xblock[django]==5.1.1
     # via
     #   -r requirements/edx/base.txt
     #   acid-xblock

xmodule/tests/test_export.py

@@ -143,9 +143,22 @@ class RoundTripTestCase(unittest.TestCase):
 
         print("Checking block equality")
         for location in initial_import.modules[course_id].keys():
-            print(("Checking", location))
-            assert blocks_are_equivalent(initial_import.modules[course_id][location],
-                                         second_import.modules[course_id][location])
+            initial_block = initial_import.modules[course_id][location]
+            reimported_block = second_import.modules[course_id][location]
+            if location.block_type == "error":
+                # Error blocks store their stacktrace as a field on the block
+                # itself. We cache failed XBlock tag -> class lookups, so a
+                # PluginError raised from the uncached state vs cached state
+                # will generate different stacktraces, making the two blocks
+                # "different" as far as blocks_are_equivalent() is concerned. It
+                # doesn't *really* matter if the stacktraces are different
+                # though, so we'll do a much less thorough comparison for error
+                # blocks:
+                assert type(initial_block) == type(reimported_block)  # pylint:disable=unidiomatic-typecheck
+                assert initial_block.display_name == reimported_block.display_name
+            else:
+                print(("Checking", location))
+                assert blocks_are_equivalent(initial_block, reimported_block)
 
 
 class TestEdxJsonEncoder(unittest.TestCase):