import: Replace generic Exception with CommandError.

This change improves error handling in `do_import_realm` by replacing
the use of a generic Exception with CommandError. The updated approach
provides clearer, user-friendly error messages when there is a version
mismatch between the exported data and the Zulip server.

Fixes zulip#32292.

zerver/lib/import_realm.py

@@ -13,6 +13,7 @@
 from bs4 import BeautifulSoup
 from django.conf import settings
 from django.core.cache import cache
+from django.core.management.base import CommandError
 from django.core.validators import validate_email
 from django.db import connection, transaction
 from django.db.backends.utils import CursorWrapper
@@ -2122,10 +2123,10 @@ def check_migration_status(exported_migration_status: MigrationStatusJson) -> No
     exported_primary_version = exported_migration_status["zulip_version"].split(".")[0]
     local_primary_version = local_migration_status["zulip_version"].split(".")[0]
     if exported_primary_version != local_primary_version:
-        raise Exception(
-            "Export was generated on a different Zulip major version.\n"
-            f"Export={exported_migration_status['zulip_version']}\n"
-            f"Server={local_migration_status['zulip_version']}"
+        raise CommandError(
+            "Error: Export was generated on a different Zulip major version.\n"
+            f"Export version: {exported_migration_status['zulip_version']}\n"
+            f"Server version: {local_migration_status['zulip_version']}"
         )
     exported_migrations_by_app = exported_migration_status["migrations_by_app"]
     local_migrations_by_app = local_migration_status["migrations_by_app"]
@@ -2160,13 +2161,13 @@ def check_migration_status(exported_migration_status: MigrationStatusJson) -> No
         ]
 
         error_message = (
-            "Export was generated on a different Zulip version.\n"
-            f"Export={exported_migration_status['zulip_version']}\n"
-            f"Server={local_migration_status['zulip_version']}\n"
+            "Error: Export was generated on a different Zulip version.\n"
+            f"Export version: {exported_migration_status['zulip_version']}\n"
+            f"Server version: {local_migration_status['zulip_version']}\n"
             "\n"
             "Database formats differ between the exported realm and this server.\n"
             "Printing migrations that differ between the versions:\n"
             "--- exported realm\n"
             "+++ this server"
         ) + "\n".join(sorted_error_log)
-        raise Exception(error_message)
+        raise CommandError(error_message)

zerver/tests/fixtures/import_fixtures/check_migrations_errors/extra_migrations_error.txt

@@ -1,6 +1,6 @@
-Export was generated on a different Zulip version.
-Export={version_placeholder}
-Server={version_placeholder}
+Error: Export was generated on a different Zulip version.
+Export version: {version_placeholder}
+Server version: {version_placeholder}
 
 Database formats differ between the exported realm and this server.
 Printing migrations that differ between the versions:

zerver/tests/fixtures/import_fixtures/check_migrations_errors/unapplied_migrations_error.txt

@@ -1,6 +1,6 @@
-Export was generated on a different Zulip version.
-Export={version_placeholder}
-Server={version_placeholder}
+Error: Export was generated on a different Zulip version.
+Export version: {version_placeholder}
+Server version: {version_placeholder}
 
 Database formats differ between the exported realm and this server.
 Printing migrations that differ between the versions:

zerver/tests/test_import_export.py

@@ -11,6 +11,7 @@
 import orjson
 from django.conf import settings
 from django.core.exceptions import ValidationError
+from django.core.management.base import CommandError
 from django.db.models import Q, QuerySet
 from django.utils.timezone import now as timezone_now
 from typing_extensions import override
@@ -2199,17 +2200,17 @@ def test_import_realm_with_different_stated_zulip_version(self) -> None:
 
         with (
             patch("zerver.lib.import_realm.ZULIP_VERSION", "8.0"),
-            self.assertRaises(Exception) as e,
+            self.assertRaises(CommandError) as e,
             self.assertLogs(level="INFO"),
         ):
             do_import_realm(
                 get_output_dir(),
                 "test-zulip",
             )
         expected_error_message = (
-            "Export was generated on a different Zulip major version.\n"
-            f"Export={ZULIP_VERSION}\n"
-            "Server=8.0"
+            "Error: Export was generated on a different Zulip major version.\n"
+            f"Export version: {ZULIP_VERSION}\n"
+            "Server version: 8.0"
         )
         self.assertEqual(expected_error_message, str(e.exception))