Add Exception Handling for Client Misconfiguration

samcli/commands/exceptions.py

@@ -18,3 +18,9 @@ class CredentialsError(UserException):
     """
     Exception class when credentials that have been passed are invalid.
     """
+
+
+class RegionError(UserException):
+    """
+    Exception class when no valid region is passed to a client.
+    """

samcli/lib/bootstrap/bootstrap.py

@@ -7,21 +7,29 @@
 import boto3
 
 from botocore.config import Config
-from botocore.exceptions import ClientError
+from botocore.exceptions import ClientError, NoRegionError, NoCredentialsError
 
 from samcli import __version__
 from samcli.cli.global_config import GlobalConfig
-from samcli.commands.exceptions import UserException
+from samcli.commands.exceptions import UserException, CredentialsError, RegionError
 
 
 LOG = logging.getLogger(__name__)
 SAM_CLI_STACK_NAME = "aws-sam-cli-managed-stack"
 
 
 def manage_stack(profile, region):
-    session = boto3.Session(profile_name=profile if profile else None)
-    cloudformation_client = session.client("cloudformation", config=Config(region_name=region if region else None))
-
+    try:
+        session = boto3.Session(profile_name=profile if profile else None)
+        cloudformation_client = session.client("cloudformation", config=Config(region_name=region if region else None))
+    except NoCredentialsError:
+        raise CredentialsError(
+            "Error Setting Up Managed Stack Client: Unable to resolve credentials for the AWS SDK for Python client. Please see their documentation for options to pass in credentials: https://boto3.amazonaws.com/v1/documentation/api/latest/guide/configuration.html"
+        )
+    except NoRegionError:
+        raise RegionError(
+            "Error Setting Up Managed Stack Client: Unable to resolve a region. Please provide a region via the --region parameter or by the AWS_REGION environment variable."
+        )
     return _create_or_get_stack(cloudformation_client)
 
 

tests/unit/lib/bootstrap/test_bootstrap.py

@@ -1,19 +1,36 @@
 from unittest import TestCase
+from unittest.mock import patch, Mock
 
 import botocore.session
 
-from botocore.exceptions import ClientError
+from botocore.exceptions import ClientError, NoCredentialsError, NoRegionError
 from botocore.stub import Stubber
 
-from samcli.commands.exceptions import UserException
-from samcli.lib.bootstrap.bootstrap import _create_or_get_stack, _get_stack_template, SAM_CLI_STACK_NAME
+from samcli.commands.exceptions import UserException, CredentialsError, RegionError
+from samcli.lib.bootstrap.bootstrap import manage_stack, _create_or_get_stack, _get_stack_template, SAM_CLI_STACK_NAME
 
 
 class TestBootstrapManagedStack(TestCase):
     def _stubbed_cf_client(self):
         cf = botocore.session.get_session().create_client("cloudformation")
         return [cf, Stubber(cf)]
 
+    @patch("boto3.Session")
+    def test_client_missing_credentials(self, boto_mock):
+        session_mock = Mock()
+        session_mock.client.side_effect = NoCredentialsError()
+        boto_mock.return_value = session_mock
+        with self.assertRaises(CredentialsError):
+            manage_stack("testprofile", "fake-region")
+
+    @patch("boto3.Session")
+    def test_client_missing_region(self, boto_mock):
+        session_mock = Mock()
+        session_mock.client.side_effect = NoRegionError()
+        boto_mock.return_value = session_mock
+        with self.assertRaises(RegionError):
+            manage_stack("testprofile", "fake-region")
+
     def test_new_stack(self):
         stub_cf, stubber = self._stubbed_cf_client()
         # first describe_stacks call will fail