Fix: Override AM_PATH_PYTHON's default action-if-not-found

AM_PATH_PYTHON's default action aborts configure. This fix ensures that
configure follows through with a noop.

Signed-off-by: Jérémie Galarneau <jeremie.galarneau@efficios.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change default loglevel to TRACE_DEBUG_LINE

We do not want default loglevel to include tracef() debug output.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Fix: python invocation through env

This modification calls the interpreter through env instead of
directly, which should be more portable for those distros which do not install
python into /usr/bin/.

Signed-off-by: Jesper Derehag <jderehag@hotmail.com>
Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>