Is it possible to use pip to install a package from a private GitHub repository?

You can use the git+ssh URI scheme, but you must set a username. Notice the git@ part in the URI:

pip install git+ssh://git@github.com/echweb/echweb-utils.git

Also read about deploy keys.

PS: In my installation, the “git+ssh” URI scheme works only with “editable” requirements:

pip install -e URI#egg=EggName

Remember: Change the : character that git remote -v prints to a / character before using the remote’s address in the pip command:

$ git remote -v
origin  git@github.com:echweb/echweb-utils.git (fetch)
#                     ^ change this to a "https://stackoverflow.com/" character

If you forget, you will get this error:

ssh: Could not resolve hostname github.com:echweb:
         nodename nor servname provided, or not known