Unclosed tags prevent notes from syncing

The HTML of some imported articles contains unclosed tags which then prevent the notes from syncing with the Evernote servers.

I have found the following code useful for solving this problem:

``` python
# Make sure img, br, and hr tags are closed
html = re.sub(r'(', r'\1 />', content, flags=re.IGNORECASE)
html = re.sub(r'(', r'\1 />', html, flags=re.IGNORECASE)
html = re.sub(r'(', r'\1 />', html, flags=re.IGNORECASE)

# Make sure ismap attribute is defined correctly
html = re.sub(r'\sismap\s', ' ismap="ismap" ', html, flags=re.IGNORECASE)
```

Unfortunately, I still have an issue syncing notes that contain iframes. The Evernote Activity Log says:
EDAMUserException: errorCode=ENML_VALIDATION parameter="Element type "iframe" must be declared."

Start from the HTML normalization code described in the issue and trace the import path that sends article notes to Evernote. Reproduce the failure with an imported note containing an iframe, then consult the Evernote Activity Log and ENML validation behavior. Done means affected notes sync successfully without the reported validation error.

Written by the indexing model from the issue text.