Option to force the progress bar

[jmd-dk]

What's the problem this feature will solve?
As described here, pip seems to automatically detect when its output is not going to a TTY, in which case it disables the progress bar during downloads. It would be nice to have an option to force the progress bar anyway.
This is a desirable feature when using pip from within scripts which want to log the output while still showing the progress bar.

Examples:

pip download --no-cache-dir                   scipy            # ✅ progress bar
pip download --no-cache-dir --progress-bar=on scipy            # ✅ progress bar
pip download --no-cache-dir                   scipy | tee log  # ❌ progress bar
pip download --no-cache-dir --progress-bar=on scipy | tee log  # ❌ progress bar

(remember to remove the downloads after running each command).

Describe the solution you'd like
Taking inspiration from wget (where the exact same situation arise), one could allow for an additional suffix :force on the values of the --progress-bar option (currently off|on|ascii|pretty|emoji).
To force the progress bar in the previous example would then look like:

pip download --no-cache-dir --progress-bar=on:force scipy | tee log

Alternative Solutions
If adding functionality to the existing --progress-bar option is considered bad, one can always invent a whole new option, e.g.

pip download --no-cache-dir --force-progress-bar scipy | tee log