bug#30616: automake-1.16: aclocal is unable to process AM_PATH_PYTHON with variable as value

[Andriy Perev Ortkin]

it fails to bootstrap util-linux too, same error.
The following commit seems to be the cause:
http://git.savannah.gnu.org/cgit/automake.git/commit/m4/python.m4?id=1d60fb72168e62d33fe433380af621de64e22f23

Reverting it solves the issue for me.