bpo-24888: Clarify subprocess.check_call propagates exceptions if unable to start process (GH-28018) (GH-28223)

(cherry picked from commit 19a304b)

Co-authored-by: DonnaDia <[email protected]>

Author: miss-islington

Doc/library/subprocess.rst

@@ -1125,6 +1125,8 @@ calls these functions.
    code was zero then return, otherwise raise :exc:`CalledProcessError`. The
    :exc:`CalledProcessError` object will have the return code in the
    :attr:`~CalledProcessError.returncode` attribute.
+   If :func:`check_call` was unable to start the process it will propagate the exception
+   that was raised.
 
    Code needing to capture stdout or stderr should use :func:`run` instead::