- Refusal, non-zero exit and timeout now raise InstallError (pm/client.py
catches only InstallError; TimeoutExpired escaped entirely). The off-Windows
refusal names a real remedy instead of the generic 'retry'.
- stdin/stdout/stderr -> DEVNULL: with capture_output the stub's RunProgram
children inherit the pipes and hold run() open past the stub's exit (and
CPython re-communicates without a timeout after a kill). The stub prints
nothing under -y, so the output tail was dead code.
- TemporaryDirectory(ignore_cleanup_errors) as in Npm.unpack; unpack empties
its destination like extract(); drop redundant local imports.
- Tests: CompletedProcess over hand-rolled stubs, no raising=False, timeout
case added, change-detector pin-suffix test removed.
084645fba4