The installation instructions on macOS suggest:

$ brew tap pegasus-isi/tools
$ brew install pegasus htcondor

This does not work anymore. After the `tap` this is the output when trying to install:

$ brew install pegasus
==> Searching for similarly named formulae...
These similarly named formulae were found:
pegasus-isi/tools/htcondor ✔ pegasus-isi/tools/pegasus@4 pegasus-isi/tools/pegasus@5
To install one of them, run (for example):
brew install pegasus-isi/tools/htcondor ✔
Error: No available formula or cask with the name "pegasus".
==> Searching taps on GitHub...
Error: No formulae found in taps.

For some reason not even brew's suggested installation command works:

$ brew install pegasus-isi/tools/pegasus@5
==> Searching for similarly named formulae...
Error: No similarly named formulae found.
Error: No available formula or cask with the name "pegasus-isi/tools/pegasus@5".

This did work for pegasus-isi/tools/htcondor, but not for pegasus-isi/tools/pegasus@5.