Module not found error if config does not exist in tools folder

[giper45]

When list_tools() is performed, RAUDI does not check if a config.py exist inside the tools/.
It gives an exception taht should be managed:

Steps to reproduce the behavior.

• Create a new folder in tools without config.py.
• Run raudi --list

Expected behavior
Raudi should show an error message if config.py or Dockerfile does not exist.

A clear and concise description of what you expected to happen.

Possible solutions
Check for the existence of config.py and Dockerfile in a check_tools function when list and build_all methods are called.
It would be useful to implement a test suite to manage and track these fail conditions.