From c5c57efbb5d08828dea08822c90b292d0d183cdb Mon Sep 17 00:00:00 2001
From: TheDooner64 <rmuldoon@yipitdata.com>
Date: Wed, 11 Jul 2018 11:39:40 -0400
Subject: [PATCH] Creating a database that already exists in the glue data
 catalog raises an exception

---
 moto/glue/exceptions.py             | 16 +++++++++++-----
 moto/glue/models.py                 |  4 ++++
 tests/test_glue/test_datacatalog.py | 14 ++++++++++++++
 3 files changed, 29 insertions(+), 5 deletions(-)

diff --git a/moto/glue/exceptions.py b/moto/glue/exceptions.py
index 0c8760f1..2f9d16d2 100644
--- a/moto/glue/exceptions.py
+++ b/moto/glue/exceptions.py
@@ -1,9 +1,15 @@
 from __future__ import unicode_literals
-from moto.core.exceptions import RESTError
+from moto.core.exceptions import JsonRESTError
 
 
-class GlueClientError(RESTError):
+class GlueClientError(JsonRESTError):
+    code = 400
 
-    def __init__(self, *args, **kwargs):
-        kwargs.setdefault('template', 'single_error')
-        super(GlueClientError, self).__init__(*args, **kwargs)
+
+class DatabaseAlreadyExistsException(GlueClientError):
+    def __init__(self):
+        self.code = 400
+        super(DatabaseAlreadyExistsException, self).__init__(
+            'DatabaseAlreadyExistsException',
+            'Database already exists.'
+        )
diff --git a/moto/glue/models.py b/moto/glue/models.py
index 55cd46bc..357a2a52 100644
--- a/moto/glue/models.py
+++ b/moto/glue/models.py
@@ -2,6 +2,7 @@ from __future__ import unicode_literals
 
 from moto.core import BaseBackend, BaseModel
 from moto.compat import OrderedDict
+from.exceptions import DatabaseAlreadyExistsException
 
 
 class GlueBackend(BaseBackend):
@@ -10,6 +11,9 @@ class GlueBackend(BaseBackend):
         self.databases = OrderedDict()
 
     def create_database(self, database_name):
+        if database_name in self.databases:
+            raise DatabaseAlreadyExistsException()
+
         database = FakeDatabase(database_name)
         self.databases[database_name] = database
         return database
diff --git a/tests/test_glue/test_datacatalog.py b/tests/test_glue/test_datacatalog.py
index 77ad1c01..c7cdb1a7 100644
--- a/tests/test_glue/test_datacatalog.py
+++ b/tests/test_glue/test_datacatalog.py
@@ -1,7 +1,9 @@
 from __future__ import unicode_literals
 
 import sure  # noqa
+from nose.tools import assert_raises
 import boto3
+from botocore.client import ClientError
 
 from moto import mock_glue
 
@@ -28,3 +30,15 @@ def test_create_database():
     database = response['Database']
 
     database.should.equal({'Name': database_name})
+
+
+@mock_glue
+def test_create_database_already_exists():
+    client = boto3.client('glue', region_name='us-east-1')
+    database_name = 'anewdatabase'
+    create_database(client, database_name)
+
+    with assert_raises(ClientError) as exc:
+        create_database(client, database_name)
+
+    exc.exception.response['Error']['Code'].should.equal('DatabaseAlreadyExistsException')