Amp forms

**Please only file reports about bugs in AMP here.**

- If you have questions about how to use AMP or other general questions about AMP please ask them on Stack Overflow under the AMP HTML tag instead of filing an issue here: http://stackoverflow.com/questions/tagged/amp-html
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If you have a bug for AMP please fill in the following template. Delete everything except the headers (including this text).

## What's the issue?

Briefly describe the bug.

action is not working inside the tag

## How do we reproduce the issue?

use amp-form and use action attribute inside it, would throw the error in the amp playground.

Please provide a public URL and ideally a reduced test case (e.g. on jsbin.com) that exhibits only your issue and nothing else. Provide step-by-step instructions for reproducing the issue:

1. Step 1 to reproduce
2. Step 2 to reproduce
3. …

## What browsers are affected?

All browsers? Some specific browser? What device type?

## Which AMP version is affected?

Is this a new issue? Or was it always broken? Paste the version of AMP where you saw this issue. (You can find the version printed in your browser's console.)

Start by reproducing the reported error in the AMP Playground using an amp-form with an action attribute. The issue provides no affected browser, AMP version, public URL, file, or test; first establish those details and define done as the action working without the reported error.

Written by the indexing model from the issue text.