How to uninstall a package installed with pip install --user

Having tested this using Python 3.5 and pip 7.1.2 on Linux, the situation appears to be this:

• pip install --user some package installs to $HOME/.local, and uninstalling it does work using pip uninstall package.
  
• It is true whether or not some Pip packages are also installed system-wide at the same time.
  
• If the pip uninstall package is installed at both places, only the local one will be uninstalled. To uninstall the package system-wide using pip, first uninstall it locally, then run the same uninstall command again, with root privileges.
  
• In addition to the predefined user install directory, pip install --target somedir some package will install the package into somedir. There is no way to uninstall a package from such a place using pip. (But there is a somewhat old unmerged pull request on Github that implements pip uninstall --target.)
  
• Since the only places pip will ever uninstall from are system-wide and predefined user-local, you need to run pip uninstall as the respective user to uninstall from a given user's local install directory.