Adding a new exercise with a description longer than 2k fails silently

[adrianlzt]

Steps to Reproduce

1. Create an exercise with more than 2k chars
   

2. Click on Submit exercise

Expected results:
The UI should limit the number of chars.
Also, if that limit is excedeed, the UI should return the error and allow the user to correct and re-submit.

Actual results:
The exercise is not created (actually, the base exercise is created, but not the translation).

Error seen in the request to create the translation:

description: ["Ensure this field has no more than 2000 characters."]

[joaogdfaero]

Could I work on this?

[rolandgeider]

Sure @joaogdfaero go ahead!

[rolandgeider]

(to make it clear, the upper limit should be 2000 characters)