Fix integ test failure

It's possible that a profile does not exist and therefore
the cred provider cannot be retrieved.  If this is the case
then we just shouldn't register the assume role provider.

awscli/customizations/assumerole.py

@@ -32,8 +32,14 @@ def inject_assume_role_provider(session, event_name, **kwargs):
         # before we start injecting things into the session.
         return
     provider = create_assume_role_provider(session)
-    session.get_component('credential_provider').insert_before(
-        'config-file', provider)
+    try:
+        session.get_component('credential_provider').insert_before(
+            'config-file', provider)
+    except Exception:
+        # This is ok, it just means that we couldn't create the credential
+        # provider object.
+        LOG.debug("Not registering assume-role provider, credential "
+                  "provider from session could not be created.")
 
 
 def create_assume_role_provider(session):

tests/unit/customizations/test_assumerole.py

@@ -55,6 +55,15 @@ def test_assume_role_provider_registration(self):
         # be registered.
         session.get_component.assert_called_with('credential_provider')
 
+    def test_provider_not_registered_on_error(self):
+        session = mock.Mock()
+        session.get_component.side_effect = Exception(
+            "Couldn't get credential_provider.")
+        assumerole.inject_assume_role_provider(
+            session, event_name='building-command-table.foo')
+        self.assertFalse(
+            session.get_component.return_value.insert_before.called)
+
 
 class TestAssumeRoleCredentialProvider(unittest.TestCase):