Modification of describe_gateways key so that it is consistent with w… (#2936)

* Modification of describe_gateways key so that it is consistent with what create_gateway returns.
Also added AnsibleModule spec to require bgp_ip on state=present as defined in the doc

* Don't remove CustomerGateways key to preserve backward compatibility

lib/ansible/modules/extras/cloud/amazon/ec2_customer_gateway.py

@@ -44,6 +44,9 @@ options:
     required: false
     default: present
     choices: [ 'present', 'absent' ]
+notes:
+    - Return values contain customer_gateway and customer_gateways keys which are identical dicts. You should use
+      customer_gateway. See U(https://github.com/ansible/ansible-modules-extras/issues/2773) for details.
 extends_documentation_fragment:
     - aws
     - ec2
@@ -182,6 +185,7 @@ class Ec2CustomerGatewayManager:
         )
         return response
 
+
 def main():
     argument_spec = ec2_argument_spec()
     argument_spec.update(
@@ -193,7 +197,12 @@ def main():
         )
     )
 
-    module = AnsibleModule(argument_spec=argument_spec, supports_check_mode=True)
+    module = AnsibleModule(argument_spec=argument_spec,
+                           supports_check_mode=True,
+                           required_if=[
+                               ('state', 'present', ['bgp_arn'])
+                           ]
+                           )
 
     if not HAS_BOTOCORE:
         module.fail_json(msg='botocore is required.')
@@ -208,19 +217,22 @@ def main():
     name = module.params.get('name')
 
     existing = gw_mgr.describe_gateways(module.params['ip_address'])
+    # describe_gateways returns a key of CustomerGateways where as create_gateway returns a
+    # key of CustomerGateway. For consistency, change it here
+    existing['CustomerGateway'] = existing['CustomerGateways']
 
     results = dict(changed=False)
     if module.params['state'] == 'present':
-        if existing['CustomerGateways']:
+        if existing['CustomerGateway']:
             results['gateway'] = existing
-            if existing['CustomerGateways'][0]['Tags']:
-                tag_array = existing['CustomerGateways'][0]['Tags']
+            if existing['CustomerGateway'][0]['Tags']:
+                tag_array = existing['CustomerGateway'][0]['Tags']
                 for key, value in enumerate(tag_array):
                     if value['Key'] == 'Name':
                         current_name = value['Value']
                         if current_name != name:
                             results['name'] = gw_mgr.tag_cgw_name(
-                                results['gateway']['CustomerGateways'][0]['CustomerGatewayId'],
+                                results['gateway']['CustomerGateway'][0]['CustomerGatewayId'],
                                 module.params['name'],
                             )
                             results['changed'] = True
@@ -237,11 +249,11 @@ def main():
             results['changed'] = True
 
     elif module.params['state'] == 'absent':
-        if existing['CustomerGateways']:
+        if existing['CustomerGateway']:
             results['gateway'] = existing
             if not module.check_mode:
                 results['gateway'] = gw_mgr.ensure_cgw_absent(
-                    existing['CustomerGateways'][0]['CustomerGatewayId']
+                    existing['CustomerGateway'][0]['CustomerGatewayId']
                 )
             results['changed'] = True