Use the correct python lib directory to install python libraries

automake does not provide the python lib directory anymore which was dealing
to install python modules in the wrong directory for Ubuntu.

Use distutils as recommended by automake

From aclocal.4

  dnl pythondir -- where to install python scripts.  This is the
  dnl   site-packages directory, not the python standard library
  dnl   directory like in previous automake betas.  This behavior
  dnl   is more consistent with lispdir.m4 for example.
  dnl Query distutils for this directory.

Signed-off-by: Aline Manera <aline.manera@gmail.com>

configure.ac

@@ -54,6 +54,8 @@ AC_SUBST([PYTHON_VERSION])
 AM_GNU_GETTEXT([external])
 AM_GNU_GETTEXT_VERSION([0.10])
 AC_PATH_PROG([CHEETAH], [cheetah], [/usr/bin/cheetah])
+AC_SUBST([pythondir],
+         [m4_esyscmd([python3 -c "import distutils.sysconfig as sys; print(sys.get_python_lib())"])])
 
 # Checking for pyflakes
 AC_PATH_PROG([PYFLAKES], [pyflakes])