fix a bug that breaks inventory updates if no credential is supplied

see: #7206

awx/main/tasks.py

@@ -481,14 +481,14 @@ class BaseTask(Task):
                 if 'OPENSSH PRIVATE KEY' in data and not openssh_keys_supported:
                     raise RuntimeError(OPENSSH_KEY_ERROR)
             for credential, data in private_data.get('credentials', {}).iteritems():
-                name = 'credential_%d' % credential.pk
                 # OpenSSH formatted keys must have a trailing newline to be
                 # accepted by ssh-add.
                 if 'OPENSSH PRIVATE KEY' in data and not data.endswith('\n'):
                     data += '\n'
                 # For credentials used with ssh-add, write to a named pipe which
                 # will be read then closed, instead of leaving the SSH key on disk.
-                if credential.kind in ('ssh', 'scm') and not ssh_too_old:
+                if credential and credential.kind in ('ssh', 'scm') and not ssh_too_old:
+                    name = 'credential_%d' % credential.pk
                     path = os.path.join(kwargs['private_data_dir'], name)
                     run.open_fifo_write(path, data)
                     private_data_files['credentials']['ssh'] = path

awx/main/tests/unit/test_tasks.py

@@ -1165,6 +1165,24 @@ class TestInventoryUpdateCredentials(TestJobExecution):
             )
         )
 
+    def test_source_without_credential(self):
+        self.instance.source = 'ec2'
+
+        def run_pexpect_side_effect(*args, **kwargs):
+            args, cwd, env, stdout = args
+
+            assert 'AWS_ACCESS_KEY_ID' not in env
+            assert 'AWS_SECRET_ACCESS_KEY' not in env
+            assert 'EC2_INI_PATH' in env
+
+            config = ConfigParser.ConfigParser()
+            config.read(env['EC2_INI_PATH'])
+            assert 'ec2' in config.sections()
+            return ['successful', 0]
+
+        self.run_pexpect.side_effect = run_pexpect_side_effect
+        self.task.run(self.pk)
+
     def test_ec2_source(self):
         aws = CredentialType.defaults['aws']()
         self.instance.source = 'ec2'