Remove custom item retrieval in the params object

[pevogam]

Not only does this hide a proper stack trace of where the missing
parameter was detected but it also makes it impossible to use
other useful methods like pop() with a default and so on, all
because of the unnecessary custom ParamNotFound error which is
never caught in an exception clause at the abc collection on
a higher level.

Signed-off-by: Plamen Dimitrov [email protected]

[pevogam]

Some more comments:

• This pull request is a suggestion that I am open about discussing. There might be better approaches than the one I had to do in order to make my own debugging easier and restore the functionality that was previously available.
• AFAIK such problems can be reproduced on python3 and not python2 due to changes in the collections modules.