As a user, I can whitelist packages to sync with standard python syntax
This story is to use the syntax from python requirements files to specify which packages should be synced. This story does NOT include directly uploading a requirements.txt (though that feature could be discussed in another issue)
It doesn't make sense for Pulp to support all of the possible syntaxes in a requirements file (like specifying a local file).
At the time of writing, pulp-python only supports a whitelist of project names, but this whitelist should become more granular and flexible.
It would be ideal to support multiple levels of filtering:
- project name
- version specifiers (including gt, lt, range)
- specific python distributions (specified by hash) 
Allowing users to specify python distributions by hashes  will significantly improve 2 of our use cases:
- reproducible, deterministic builds
- improved security
These ideas are related to the implementation of this story, but if they are accepted, they should be filed separately.
- Create a whitelist from a requirements.txt
- Create a whitelist from a Pipfile (pipenv)
- Create a whitelist from a Pipfile.lock (pipenv)
- Create a whitelist from a python toml file