[qa] Remove misleading "errorString syntax"

[MarcoFalke]

Personally, I find the errorString "syntax" to "see" when an exception happens confusing. It is error prone in the best case.

Imo, valid syntax is either

try:
  something()
  assert(False)
except:
  assert(thing())

or

try:
  something()
except:
  assert(thing())
else:
  assert(False)

[laanwj]

ACK ffff866