Show warning if no media_[provider] modules are enabled

The patch is created correctly and technically gets the job done, but this message will always show up. What about using an approach more like FullCalendar's install check for the

http://drupalcode.org/project/fullcalendar.git/blob/refs/heads/7.x-2.x:/...
http://drupalcode.org/project/fullcalendar.git/blob/refs/heads/7.x-2.x:/...

the _fullcalendar_status() uses...

if (!file_exists($path)) {
  return FALSE;
}

Instead of checking for a specific file, we could loop through an array of media_ modules cm_vod_feed might be use with using module_exists(). If none of these modules are enabled when you try to enable cm_vod_feed, it will fail with error like what you added.... but once the user enables any of those media_[provider] modules, the user will be able to enable cm_vod_feed.

Make sense?

Really sorry I didn't see that you updated this patch until now.

This check needs to be in a hook other than init. That get's called on every page load so it's checking way too often even after the modules exist. Every time a user clicks something Drupal would be asking...

Are media_ modules enabled? Yes. Ok, do nothing.
Are media_ modules enabled? Yes. Ok, do nothing.
Are media_ modules enabled? Yes. Ok, do nothing.
Are media_ modules enabled? Yes. Ok, do nothing.
Are media_ modules enabled? Yes. Ok, do nothing.

That doesn't really cost us a lot in terms of CPU or RAM, but it all adds up. If every module was doing that, Drupal would get very slow. Instead I moved the function you wrote to the .install so that it is only checking on install and on the status page.

There are still a few issues with this patch.

1) The warning shows up above the status report in addition to in the status report
2) We are checking for media_archive twice and aren't checking for dozens of other media_ modules

If you can get those issues resolved, I can commit this and you'll get your first commit credit on your user profile https://drupal.org/user/2734505.