taskw fails when taskrc has environment variables

[austb]

Taskrc supports environment variables in it config https://taskwarrior.org/docs/man/taskrc.5/

Note that environment variables are also expanded in paths (and any other taskrc variables).

This error is from a bugwarrior-pull

Traceback (most recent call last):
 File "/home/austb/.local/bin/bugwarrior-pull", line 7, in <module>
 sys.exit(pull())
 ^^^^^^
 ...
 File "/home/austb/.local/share/pipx/venvs/bugwarrior/lib/python3.11/site-packages/taskw/taskrc.py", line 57, in __init__
 config = self._read(self.path)
 ^^^^^^^^^^^^^^^^^^^^^
 File "/home/austb/.local/share/pipx/venvs/bugwarrior/lib/python3.11/site-packages/taskw/taskrc.py", line 105, in _read
 TaskRc(right.strip())
 File "/home/austb/.local/share/pipx/venvs/bugwarrior/lib/python3.11/site-packages/taskw/taskrc.py", line 57, in __init__
 config = self._read(self.path)
 ^^^^^^^^^^^^^^^^^^^^^
 File "/home/austb/.local/share/pipx/venvs/bugwarrior/lib/python3.11/site-packages/taskw/taskrc.py", line 95, in _read
 with open(path, 'r') as config_file:
 ^^^^^^^^^^^^^^^
FileNotFoundError: [Errno 2] No such file or directory: '$HOME/.config/task/$AUSTB_HOSTNAME_SHORT/bugwarrior-uda.conf'