When python is available, run the commandline unit tests from "make check"

changes/python-tests

+  o Minor features:
+    - "make check" now runs extra tests beyond the unit test scripts if
+      Python is installed.
+

configure.ac

@@ -183,6 +183,13 @@ AM_CONDITIONAL(NAT_PMP, test x$natpmp = xtrue)
 AM_CONDITIONAL(MINIUPNPC, test x$upnp = xtrue)
 AM_PROG_CC_C_O
 
+AC_ARG_VAR(PYTHON)
+AC_CHECK_PROGS(PYTHON, [python python2 python3])
+if test "x$PYTHON" = "x"; then
+  AC_MSG_WARN([Python unavailable; some tests will not be run.])
+fi
+AM_CONDITIONAL(USEPYTHON, [test "x$PYTHON" != "x"])
+
 ifdef([AC_C_FLEXIBLE_ARRAY_MEMBER], [
 AC_C_FLEXIBLE_ARRAY_MEMBER
 ], [

src/test/include.am

-TESTS+= src/test/test
+TESTS += src/test/test
 
 noinst_PROGRAMS+= src/test/bench
 if UNITTESTS_ENABLED
@@ -77,3 +77,8 @@ src_test_test_ntor_cl_AM_CPPFLAGS =	       \
 
 endif
 
+check-local:
+if USEPYTHON
+	$(PYTHON) src/test/test_cmdline_args.py
+endif
+