Fix issue2551129 - Template not found return 500 and traceback Handle traceback caused when requested @template is not found. Moved scope of try to include call to self.selectTemplate. Patch provided by Cedric Krier. Additional patch to make this case return 400 error since it is a client caused error. Test case added.

try:
    # Python 2.
    my_input = raw_input
except NameError:
    # Python 3+.
    my_input = input