moz-phab was working previously. I ran it today, it self-updated, and then fails with some error in glean. Full log below. Running the command again continues to fail (obviously it doesn't self-update again, but emits the same python backtrace).

$ moz-phab submit master bd30abaefe473
Upgrading to version 0.1.91
Collecting MozPhab
  Downloading MozPhab-0.1.91.tar.gz (73 kB)
     |████████████████████████████████| 73 kB 2.4 MB/s 
Requirement already satisfied, skipping upgrade: distro in /usr/lib/python3/dist-packages (from MozPhab) (1.4.0)
Requirement already satisfied, skipping upgrade: glean-sdk>=31.0.0 in /home/kats/.local/lib/python3.8/site-packages (from MozPhab) (33.0.1)
Collecting python-hglib==2.6.1
  Downloading python-hglib-2.6.1.tar.gz (34 kB)
Requirement already satisfied, skipping upgrade: sentry-sdk>=0.14.3 in /home/kats/.local/lib/python3.8/site-packages (from MozPhab) (0.17.8)
Requirement already satisfied, skipping upgrade: setuptools in /usr/lib/python3/dist-packages (from MozPhab) (45.2.0)
Requirement already satisfied, skipping upgrade: cffi>=1 in /home/kats/.local/lib/python3.8/site-packages (from glean-sdk>=31.0.0->MozPhab) (1.14.3)
Requirement already satisfied, skipping upgrade: glean-parser==1.28.6 in /home/kats/.local/lib/python3.8/site-packages (from glean-sdk>=31.0.0->MozPhab) (1.28.6)
Requirement already satisfied, skipping upgrade: certifi in /usr/lib/python3/dist-packages (from sentry-sdk>=0.14.3->MozPhab) (2019.11.28)
Requirement already satisfied, skipping upgrade: urllib3>=1.10.0 in /usr/lib/python3/dist-packages (from sentry-sdk>=0.14.3->MozPhab) (1.25.8)
Requirement already satisfied, skipping upgrade: pycparser in /home/kats/.local/lib/python3.8/site-packages (from cffi>=1->glean-sdk>=31.0.0->MozPhab) (2.20)
Requirement already satisfied, skipping upgrade: diskcache>=4 in /home/kats/.local/lib/python3.8/site-packages (from glean-parser==1.28.6->glean-sdk>=31.0.0->MozPhab) (5.0.3)
Requirement already satisfied, skipping upgrade: appdirs>=1.4 in /home/kats/.local/lib/python3.8/site-packages (from glean-parser==1.28.6->glean-sdk>=31.0.0->MozPhab) (1.4.4)
Requirement already satisfied, skipping upgrade: PyYAML>=3.13 in /usr/lib/python3/dist-packages (from glean-parser==1.28.6->glean-sdk>=31.0.0->MozPhab) (5.3.1)
Requirement already satisfied, skipping upgrade: Click>=7 in /usr/lib/python3/dist-packages (from glean-parser==1.28.6->glean-sdk>=31.0.0->MozPhab) (7.0)
Requirement already satisfied, skipping upgrade: yamllint>=1.18.0 in /home/kats/.local/lib/python3.8/site-packages (from glean-parser==1.28.6->glean-sdk>=31.0.0->MozPhab) (1.24.2)
Requirement already satisfied, skipping upgrade: jsonschema>=3.0.2 in /home/kats/.local/lib/python3.8/site-packages (from glean-parser==1.28.6->glean-sdk>=31.0.0->MozPhab) (3.2.0)
Requirement already satisfied, skipping upgrade: Jinja2>=2.10.1 in /home/kats/.local/lib/python3.8/site-packages (from glean-parser==1.28.6->glean-sdk>=31.0.0->MozPhab) (2.11.2)
Requirement already satisfied, skipping upgrade: pathspec>=0.5.3 in /home/kats/.local/lib/python3.8/site-packages (from yamllint>=1.18.0->glean-parser==1.28.6->glean-sdk>=31.0.0->MozPhab) (0.8.0)
Requirement already satisfied, skipping upgrade: pyrsistent>=0.14.0 in /home/kats/.local/lib/python3.8/site-packages (from jsonschema>=3.0.2->glean-parser==1.28.6->glean-sdk>=31.0.0->MozPhab) (0.17.3)
Requirement already satisfied, skipping upgrade: six>=1.11.0 in /usr/lib/python3/dist-packages (from jsonschema>=3.0.2->glean-parser==1.28.6->glean-sdk>=31.0.0->MozPhab) (1.14.0)
Requirement already satisfied, skipping upgrade: attrs>=17.4.0 in /home/kats/.local/lib/python3.8/site-packages (from jsonschema>=3.0.2->glean-parser==1.28.6->glean-sdk>=31.0.0->MozPhab) (20.2.0)
Requirement already satisfied, skipping upgrade: MarkupSafe>=0.23 in /home/kats/.local/lib/python3.8/site-packages (from Jinja2>=2.10.1->glean-parser==1.28.6->glean-sdk>=31.0.0->MozPhab) (1.1.1)
Building wheels for collected packages: MozPhab, python-hglib
  Building wheel for MozPhab (setup.py) ... done
  Created wheel for MozPhab: filename=MozPhab-0.1.91-py3-none-any.whl size=86559 sha256=c81816b1ee48409c05be1aa327393b3ef7133b960094ba360caf22688f1dec2d
  Stored in directory: /tmp/pip-ephem-wheel-cache-ebfzy0kv/wheels/f9/54/c1/4569aa963825a73cb273bea63f241386fcb4b96f265d68e0c0
  Building wheel for python-hglib (setup.py) ... done
  Created wheel for python-hglib: filename=python_hglib-2.6.1-py3-none-any.whl size=23913 sha256=2cfac324d5a4df0d821a140d7d51f43544bc6b59269c8f1418dc03d48a30b2a5
  Stored in directory: /tmp/pip-ephem-wheel-cache-ebfzy0kv/wheels/20/15/23/01cdc9fffe173e6927eabdf54aa38f8cdbca2b01fc30130f70
Successfully built MozPhab python-hglib
Installing collected packages: python-hglib, MozPhab
  Attempting uninstall: MozPhab
    Found existing installation: MozPhab 0.1.90
    Uninstalling MozPhab-0.1.90:
      Successfully uninstalled MozPhab-0.1.90
Successfully installed MozPhab-0.1.91 python-hglib-2.6.1
Restarting...
Traceback (most recent call last):
  File "/home/kats/.local/bin/moz-phab", line 5, in <module>
    from mozphab.mozphab import run
  File "/home/kats/.local/lib/python3.8/site-packages/mozphab/mozphab.py", line 20, in <module>
    from .args import parse_args
  File "/home/kats/.local/lib/python3.8/site-packages/mozphab/args.py", line 14, in <module>
    from .detect_repository import find_repo_root
  File "/home/kats/.local/lib/python3.8/site-packages/mozphab/detect_repository.py", line 8, in <module>
    from .git import Git
  File "/home/kats/.local/lib/python3.8/site-packages/mozphab/git.py", line 24, in <module>
    from .telemetry import telemetry
  File "/home/kats/.local/lib/python3.8/site-packages/mozphab/telemetry.py", line 174, in <module>
    telemetry = Telemetry()
  File "/home/kats/.local/lib/python3.8/site-packages/mozphab/telemetry.py", line 46, in __init__
    self.pings = load_pings(environment.MOZPHAB_MAIN_DIR / "pings.yaml")
  File "/home/kats/.local/lib/python3.8/site-packages/glean/_loader.py", line 202, in load_pings
    metrics = load_metrics(filepath, config)
  File "/home/kats/.local/lib/python3.8/site-packages/glean/_loader.py", line 166, in load_metrics
    raise ValueError(f"Didn't find any metrics in '{filepath}'")
ValueError: Didn't find any metrics in '[PosixPath('/home/kats/.local/lib/python3.8/site-packages/mozphab/pings.yaml')]'

For now I uninstalled and reinstalled 0.1.90:

pip3 uninstall MozPhab
pip3 install MozPhab=0.1.90

and that's unblocking me.