[TYPO3-core] RFC #12117: Add some flash messages to EM

[Francois Suter]

Hi Steffen,

> Problem:
> We have flash messages now, but Extension Manager makes no use of them.
> 
> Solution:
> Turn most frequent messages into flash messages.

+1 on reading and testing.

I'll take care of the commit, but I would like to do one little change 
if you don't mind: in the case of an extension overwrite (but without 
the overwrite flag) you added an "Error" header to the flash message. It 
is not mandatory for flash messages to have a header. In this case, the 
style of the message itself indicates an error, so I find it redundant 
to add "Error" in the header. So I would like to remove the header in 
that case. Is that ok with you?

Cheers

-- 

Francois Suter
Cobweb Development Sarl - http://www.cobweb.ch