Imported, but we have problems:

Sorry about that, it was an old link. Try to insert the example in a test page..

I think this is done!

I'm developing a Texla Exception system to die gracefully in case of Parser errors, printing some useful information.

To complete this task handle the eqnarray block type in MediaWikiRenderer.py separately from the align block.
You have to modify the math content checking that between every \\ there's only one &.

@mapellidario what about keeping only one & for each line?

The problem here is that the MacroParser always searches for arguments when it reads the newcommand command. With

Fixed by spaces_check plugin