Fixes for IAM Role Description field in responses from list_roles and create_roles (#3724)

* Add IAM Role Description field to list_roles responses

The IAM ListRoles IAM API call will return the Description key/value
for each role if it exists.  If it does not exist the Description
key is not included.

* fix handling in create_role resp

* blackg

* Combine two tests using pytest.mark.parametrize

* consistency

moto/iam/responses.py

@@ -1275,7 +1275,7 @@ CREATE_ROLE_TEMPLATE = """<CreateRoleResponse xmlns="https://iam.amazonaws.com/d
       <Arn>{{ role.arn }}</Arn>
       <RoleName>{{ role.name }}</RoleName>
       <AssumeRolePolicyDocument>{{ role.assume_role_policy_document }}</AssumeRolePolicyDocument>
-      {% if role.description %}
+      {% if role.description is not none %}
       <Description>{{role.description}}</Description>
       {% endif %}
       <CreateDate>{{ role.created_iso_8601 }}</CreateDate>
@@ -1420,6 +1420,9 @@ LIST_ROLES_TEMPLATE = """<ListRolesResponse xmlns="https://iam.amazonaws.com/doc
           <PermissionsBoundaryArn>{{ role.permissions_boundary }}</PermissionsBoundaryArn>
         </PermissionsBoundary>
         {% endif %}
+        {% if role.description is not none %}
+        <Description>{{ role.description }}</Description>
+        {% endif %}
       </member>
       {% endfor %}
     </Roles>

tests/test_iam/test_iam.py

@@ -4029,6 +4029,29 @@ def test_list_roles_none_found_returns_empty_list():
     assert len(roles) == 0
 
 
+@pytest.mark.parametrize("desc", ["", "Test Description"])
+@mock_iam()
+def test_list_roles_with_description(desc):
+    conn = boto3.client("iam", region_name="us-east-1")
+    resp = conn.create_role(
+        RoleName="my-role", AssumeRolePolicyDocument="some policy", Description=desc,
+    )
+    resp.get("Role").get("Description").should.equal(desc)
+
+    # Ensure the Description is included in role listing as well
+    conn.list_roles().get("Roles")[0].get("Description").should.equal(desc)
+
+
+@mock_iam()
+def test_list_roles_without_description():
+    conn = boto3.client("iam", region_name="us-east-1")
+    resp = conn.create_role(RoleName="my-role", AssumeRolePolicyDocument="some policy",)
+    resp.get("Role").should_not.have.key("Description")
+
+    # Ensure the Description is not included in role listing as well
+    conn.list_roles().get("Roles")[0].should_not.have.key("Description")
+
+
 @mock_iam()
 def test_create_user_with_tags():
     conn = boto3.client("iam", region_name="us-east-1")