Fails when the `brew` command is not available

[S-zebra]

Distutils tries to get the output of brew --prefix, but it fails if Homebrew is not installed on the system, or when brew command is not available.

distutils/distutils/command/_framework_compat.py

Line 42 in 152c13d

homebrew_prefix = subprocess.check_output(['brew', '--prefix'], text=True).strip()

[dflems]

See also #159 and #155 (comment)

@jaraco

[jaraco]

At first, I was going to use this diff:

diff --git a/distutils/command/_framework_compat.py b/distutils/command/_framework_compat.py
index e032603..c2849a1 100644
--- a/distutils/command/_framework_compat.py
+++ b/distutils/command/_framework_compat.py
@@ -7,6 +7,7 @@ import sys
 import os
 import functools
 import subprocess
+import contextlib
 
 
 @functools.lru_cache()
@@ -39,7 +40,10 @@ schemes = dict(
 def vars():
     if not enabled():
         return {}
-    homebrew_prefix = subprocess.check_output(['brew', '--prefix'], text=True).strip()
+    with contextlib.suppress(FileNotFoundError):
+        homebrew_prefix = subprocess.check_output(
+            ['brew', '--prefix'], text=True
+        ).strip()
     return locals()

But then I realized that will only cause a different error because {homebrew_prefix} will be in the scheme but undefined. The enabled() function needs to detect whether the install is a homebrew one.

[jaraco]

Maybe the presence of "Cellar" in the projectbase config var is a good indicator?

>>> pprint.pprint({k:v for k, v in sysconfig.get_config_vars().items() if isinstance(v, str) and 'Cellar' in v})
{'projectbase': '/opt/homebrew/Cellar/python@3.10/3.10.5/Frameworks/Python.framework/Versions/3.10/bin',
 'srcdir': '/opt/homebrew/Cellar/python@3.10/3.10.5/Frameworks/Python.framework/Versions/3.10/lib/python3.10/config-3.10-darwin'}

[jaraco]

Fix is rolling out is 63.2.0.