refactor S3 exceptions to inherit from RESTError

moto/s3/exceptions.py

@@ -1,9 +1,40 @@
 from __future__ import unicode_literals
+from moto.core.exceptions import RESTError
 
 
-class BucketAlreadyExists(Exception):
+ERROR_WITH_BUCKET_NAME = """{% extends 'error' %}
+{% block extra %}<BucketName>{{ bucket }}</BucketName>{% endblock %}
+"""
+
+
+class S3ClientError(RESTError):
     pass
 
 
-class MissingBucket(Exception):
-    pass
+class BucketError(S3ClientError):
+    def __init__(self, *args, **kwargs):
+        kwargs.setdefault('template', 'bucket_error')
+        self.templates['bucket_error'] = ERROR_WITH_BUCKET_NAME
+        super(BucketError, self).__init__(*args, **kwargs)
+
+
+class BucketAlreadyExists(BucketError):
+    code = 409
+
+    def __init__(self, *args, **kwargs):
+        super(BucketAlreadyExists, self).__init__(
+            "BucketAlreadyExists",
+            ("The requested bucket name is not available. The bucket "
+             "namespace is shared by all users of the system. Please "
+             "select a different name and try again"),
+            *args, **kwargs)
+
+
+class MissingBucket(BucketError):
+    code = 404
+
+    def __init__(self, *args, **kwargs):
+        super(MissingBucket, self).__init__(
+            "NoSuchBucket",
+            "The specified bucket does not exist",
+            *args, **kwargs)