curl-prgrs causes high CPU and even may slow down downloads because of this.
Possible approaches to fix this:
- 1) find a replacement for curl-prgrs in bash, or
- 2) re-implement curl-prgrs in python, or
- 3) make torbrowser-launcher work with (Qubes-)Whonix
- 4) find a way to deprecate tb-updater by using guix (T600) or so. Or not. 
- 5) fix curl-prgrs, perhaps port it to pipeviewer pv (T649)
a) Emulate curl options in python:
--fail --tlsv1.2 --proto =https --max-time 180
b) Emulate endless data attack protection.
if [ "$bytes" -gt "$CURL_PRGRS_MAX_FILE_SIZE_BYTES" ]; then exit 81 fi
c) Emulate environment variable CURL_PRGRS_EXEC processing.
if [ "$CURL_PRGRS_EXEC" = "" ]; then true else if [ "$percent_last" = "$percent" ]; then true else percent_last="$percent" eval $CURL_PRGRS_EXEC $percent fi fi
 Keeping tb-updater has the advantage that it could relatively easily(*) transformed into a tpo-downloader, that can also fetch other software from torproject.org such as Tor Messenger.
(*) Time is an issue.