I\'m developing a Python application and in the process of branching off a release. I\'ve got a PyPI server set up on a company server and I\'ve copied a source distribution
I'm ignoring licensing issues in this answer. You definetly need to take these into account before you really do a release.
Is it acceptable to rely on third-party libraries like this in setup.py
Yes, it is acceptable but generally these should be minimized, especially if these are modules which have no obvious use for the end-user. Noone likes to have packages they don't need or use.
what is the recommended approach to using them?
There are basically 3 options:
Bootstrap them (for example use pip to programmatically install packages). For example setuptools provides an ez_setup.py file that can be used to bootstrap setuptools. Maybe that can be customized to download and install appdirs.
Include them (especially if it's a small package) in your project. For example appdirs is basically just a single file module. Pretty easy to copy and maintain in your project. Be very careful with licensing issues when you do that!
Fail gracefully when it's not possible to import them and let the user install them. For example:
try:
import appdirs
except ImportError:
raise ImportError('this package requires "appdirs" to be installed. '
'Install it first: "pip install appdirs".')