Package dependencies and optional dependencies

[victorterpstra]

Currently, the dse-do-utils doesn't define dependencies.
It is up to the user to ensure the packages it requires are installed.

In some cases, the import statement is deep in the code and will only run if the code that depends on it is executed.
For instance, folium or sqlalchemy. This avoids the install of these packages if the related functionality of the dse-do-utils is never used.

This approach works, but there might be a better option with optional dependencies:

• https://setuptools.pypa.io/en/latest/userguide/dependency_management.html#declaring-required-dependency
• https://stackoverflow.com/questions/6237946/optional-dependencies-in-distutils-pip

[victorterpstra]

This is done in setup.py with the extras_require.
See

• https://stackoverflow.com/questions/41268863/what-is-the-difference-between-extras-require-and-install-requires-in-se?rq=1

One of the extra could be 'CP4D', with requirements:

• ibm_watson_studio_lib
• decision-optimization-client
  Discussion: since these packages are either not available in PyPI and definitely cannot run outside of CP4D, what happens with projects we develop both on CP4D and on local machine?