Fallback to trying to create bucket without LocationConstraint

src/backups.py

@@ -284,13 +284,28 @@ def _create_bucket_if_not_exists(self) -> None:
         except ClientError:
             logger.warning("Bucket %s doesn't exist or you don't have access to it.", bucket_name)
             exists = False
-        if not exists:
-            try:
-                bucket.create(CreateBucketConfiguration={"LocationConstraint": region})
+        if exists:
+            return
 
-                bucket.wait_until_exists()
-                logger.info("Created bucket '%s' in region=%s", bucket_name, region)
-            except ClientError as error:
+        try:
+            bucket.create(CreateBucketConfiguration={"LocationConstraint": region})
+
+            bucket.wait_until_exists()
+            logger.info("Created bucket '%s' in region=%s", bucket_name, region)
+        except ClientError as error:
+            if error.response["Error"]["Code"] == "InvalidLocationConstraint":
+                logger.info("Specified location-constraint is not valid, trying create without it")
+                try:
+                    bucket.create()
+
+                    bucket.wait_until_exists()
+                    logger.info("Created bucket '%s', ignored region=%s", bucket_name, region)
+                except ClientError as error:
+                    logger.exception(
+                        "Couldn't create bucket named '%s' in region=%s.", bucket_name, region
+                    )
+                    raise error
+            else:
                 logger.exception(
                     "Couldn't create bucket named '%s' in region=%s.", bucket_name, region
                 )

tests/unit/test_backups.py

@@ -368,7 +368,7 @@ def test_create_bucket_if_not_exists(harness, tls_ca_chain_filename):
         # Test when the bucket doesn't exist.
         head_bucket.reset_mock()
         head_bucket.side_effect = ClientError(
-            error_response={"Error": {"Code": 1, "message": "fake error"}},
+            error_response={"Error": {"Code": "SomeFakeException", "message": "fake error"}},
             operation_name="fake operation name",
         )
         harness.charm.backup._create_bucket_if_not_exists()
@@ -381,7 +381,7 @@ def test_create_bucket_if_not_exists(harness, tls_ca_chain_filename):
         create.reset_mock()
         wait_until_exists.reset_mock()
         create.side_effect = ClientError(
-            error_response={"Error": {"Code": 1, "message": "fake error"}},
+            error_response={"Error": {"Code": "SomeFakeException", "message": "fake error"}},
             operation_name="fake operation name",
         )
         with pytest.raises(ClientError):
@@ -391,9 +391,31 @@ def test_create_bucket_if_not_exists(harness, tls_ca_chain_filename):
         create.assert_called_once()
         wait_until_exists.assert_not_called()
 
+        # Test when the bucket creation fails with InvalidLocationConstraint.
+        head_bucket.reset_mock()
+        create.reset_mock()
+        wait_until_exists.reset_mock()
+        create.side_effect = ClientError(
+            error_response={
+                "Error": {"Code": "InvalidLocationConstraint", "message": "fake error"}
+            },
+            operation_name="fake operation name",
+        )
+        with pytest.raises(ClientError):
+            harness.charm.backup._create_bucket_if_not_exists()
+            assert False
+        head_bucket.assert_called_once()
+        want = [
+            call(CreateBucketConfiguration={"LocationConstraint": "test-region"}),
+            call(),
+        ]
+        create.assert_has_calls(want)
+        wait_until_exists.assert_not_called()
+
         # Test when the bucket creation fails due to a timeout error.
         head_bucket.reset_mock()
         create.reset_mock()
+        wait_until_exists.reset_mock()
         head_bucket.side_effect = botocore.exceptions.ConnectTimeoutError(
             endpoint_url="fake endpoint URL"
         )