Return correct error when creating a bucket with empty CreateBucketConfiguration (#3079)

* Several updates to the contributor documentation with extra information.

* Fix failing test by providing a region.

* Create test for issue 2210.

* Check if CreateBucketConfiguration is supplied and empty; raise MalformedXML error if so.

CONTRIBUTING.md

@@ -1,32 +1,41 @@
-### Contributing code
+# Contributing code
 
 Moto has a [Code of Conduct](https://github.com/spulec/moto/blob/master/CODE_OF_CONDUCT.md), you can expect to be treated with respect at all times when interacting with this project.
 
 ## Running the tests locally
 
-Moto has a Makefile which has some helpful commands for getting setup. You should be able to run `make init` to install the dependencies and then `make test` to run the tests.  
+Moto has a [Makefile](./Makefile) which has some helpful commands for getting set up.
+You should be able to run `make init` to install the dependencies and then `make test` to run the tests.
+
+*NB. On first run, some tests might take a while to execute, especially the Lambda ones, because they may need to download a Docker image before they can execute.*
 
 ## Linting
+
 Run `make lint` or `black --check moto tests` to verify whether your code confirms to the guidelines.
 
-## Is there a missing feature?
+## Getting to grips with the codebase
+
+Moto maintains a list of [good first issues](https://github.com/spulec/moto/contribute) which you may want to look at before
+implementing a whole new endpoint.
+
+## Missing features
 
 Moto is easier to contribute to than you probably think. There's [a list of which endpoints have been implemented](https://github.com/spulec/moto/blob/master/IMPLEMENTATION_COVERAGE.md) and we invite you to add new endpoints to existing services or to add new services.
 
 How to teach Moto to support a new AWS endpoint:
 
-* Create an issue describing what's missing. This is where we'll all talk about the new addition and help you get it done.
+* Search for an existing [issue](https://github.com/spulec/moto/issues) that matches what you want to achieve.
+* If one doesn't already exist, create a new issue describing what's missing. This is where we'll all talk about the new addition and help you get it done.
 * Create a [pull request](https://help.github.com/articles/using-pull-requests/) and mention the issue # in the PR description.
 * Try to add a failing test case. For example, if you're trying to implement `boto3.client('acm').import_certificate()` you'll want to add a new method called `def test_import_certificate` to `tests/test_acm/test_acm.py`.
 * If you can also implement the code that gets that test passing that's great. If not, just ask the community for a hand and somebody will assist you.
 
-# Maintainers
+## Maintainers
 
-## Releasing a new version of Moto
+### Releasing a new version of Moto
 
-You'll need a PyPi account and a Dockerhub account to release Moto. After we release a new PyPi package we build and push the [motoserver/moto](https://hub.docker.com/r/motoserver/moto/) Docker image.
+You'll need a PyPi account and a DockerHub account to release Moto. After we release a new PyPi package we build and push the [motoserver/moto](https://hub.docker.com/r/motoserver/moto/) Docker image.
 
 * First, `scripts/bump_version` modifies the version and opens a PR
 * Then, merge the new pull request
 * Finally, generate and ship the new artifacts with `make publish`
-

moto/s3/responses.py

@@ -615,6 +615,19 @@ class ResponseObject(_TemplateEnvironmentMixin, ActionAuthenticatorMixin):
                 pass
         return False
 
+    def _create_bucket_configuration_is_empty(self, body):
+        if body:
+            try:
+                create_bucket_configuration = xmltodict.parse(body)[
+                    "CreateBucketConfiguration"
+                ]
+                del create_bucket_configuration["@xmlns"]
+                if len(create_bucket_configuration) == 0:
+                    return True
+            except KeyError:
+                pass
+        return False
+
     def _parse_pab_config(self, body):
         parsed_xml = xmltodict.parse(body)
         parsed_xml["PublicAccessBlockConfiguration"].pop("@xmlns", None)
@@ -733,6 +746,9 @@ class ResponseObject(_TemplateEnvironmentMixin, ActionAuthenticatorMixin):
             ):
                 raise IllegalLocationConstraintException()
             if body:
+                if self._create_bucket_configuration_is_empty(body):
+                    raise MalformedXML()
+
                 try:
                     forced_region = xmltodict.parse(body)["CreateBucketConfiguration"][
                         "LocationConstraint"

tests/test_s3/test_s3.py

@@ -1042,7 +1042,7 @@ def test_s3_object_in_public_bucket_using_multiple_presigned_urls():
 
 @mock_s3
 def test_streaming_upload_from_file_to_presigned_url():
-    s3 = boto3.resource("s3")
+    s3 = boto3.resource("s3", region_name="us-east-1")
     bucket = s3.Bucket("test-bucket")
     bucket.create()
     bucket.put_object(Body=b"ABCD", Key="file.txt")
@@ -1976,6 +1976,15 @@ def test_boto3_bucket_create_eu_central():
     )
 
 
+@mock_s3
+def test_bucket_create_empty_bucket_configuration_should_return_malformed_xml_error():
+    s3 = boto3.resource("s3", region_name="us-east-1")
+    with assert_raises(ClientError) as e:
+        s3.create_bucket(Bucket="whatever", CreateBucketConfiguration={})
+    e.exception.response["Error"]["Code"].should.equal("MalformedXML")
+    e.exception.response["ResponseMetadata"]["HTTPStatusCode"].should.equal(400)
+
+
 @mock_s3
 def test_boto3_head_object():
     s3 = boto3.resource("s3", region_name=DEFAULT_REGION_NAME)