[GRASS-dev] Unify python GRASS defined exception in one common file

[Pietro]

Dear devs,

What do you think if we unify all our custom exceptions in one common file?
Just to avoid code repetitions and help consistency.

Looking into the code I found the following custom exceptions:

{{{
$ grep --color=auto
--exclude-dir={.svn,.git,.OBJ,locale,dist.x86_64-unknown-linux-gnu}
-IrnE "class\s\w+\(Exception\)\:"
lib/python/pygrass/messages/__init__.py:21:class FatalError(Exception):
lib/python/pygrass/errors.py:11:class AbstractError(Exception):
lib/python/pygrass/errors.py:19:class ParameterError(Exception):
lib/python/pygrass/errors.py:23:class FlagError(Exception):
lib/python/pydispatch/errors.py:4:class DispatcherError(Exception):
lib/python/temporal/abstract_dataset.py:26:class ImplementationError(Exception):
lib/python/temporal/temporal_algebra.py:655:class FatalError(Exception):
lib/python/ctypes/ctypesgencore/parser/lex.py:46:class LexError(Exception):
lib/python/ctypes/ctypesgencore/parser/yacc.py:87:class
YaccError(Exception):   pass
lib/python/script/core.py:50:class ScriptError(Exception):
gui/wxpython/core/gcmd.py:156:class GException(Exception):
gui/wxpython/wxgui.py:86:class Usage(Exception):
}}}

Perhaps we could create a new file in grass.script.errors or
grass.script.exceptions, or outside script so something like
grass.errors or grass.exceptions.

Do you think it is a bad idea?

Best regards

Pietro