fix exception handling for python version < 3.6

[vipul-sharma20]

Use ImportError in place of ModuleNotFoundError

• ModuleNotFoundError was introduced from Python 3.6
• To handle import_module() exceptions for Python version below 3.6, we can use ImportError
• ImportError is a subclass of ModuleNotFoundError

Considering that this is meant to support Python 3.5 too

reference: https://docs.python.org/3/library/exceptions.html#ModuleNotFoundError

Thanks and you've done a nice work on this project.

[squeaky-pl]

Hi, yes indeed. I was coding and testing last month on 3.6 only. I would prefer this to be conditional, on py3.6 use exception I used and on py3.5 fallback to more general one. Something like

try:
 ModuleNotFoundError
except NameError
 ModuleNotFoundError = ImportError

in the beginning of the file

[vipul-sharma20]

Yes, it seems decent. Updated in the latest commit.

[squeaky-pl]

Great, so much thanks.