python tests: use py shebang instead of $(PYTHON)

I'm going to make the external tests manually launchable. For that I first had
an error message if $(PYTHON) was empty. But Pau says I should just use shebang
instead and ignore the autoconf python stuff, since that often fails anyway.

Change-Id: Ie35dd78c42577109a6a3143221a9769e47d361a5
diff --git a/tests/Makefile.am b/tests/Makefile.am
index c225afa..f6b33fc 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -46,10 +46,10 @@
 python-tests: $(BUILT_SOURCES)
 	osmotestvty.py -p $(abs_top_srcdir) -w $(abs_top_builddir) -v
 	osmotestconfig.py -p $(abs_top_srcdir) -w $(abs_top_builddir) -v
-	$(PYTHON) $(srcdir)/vty_test_runner.py -w $(abs_top_builddir) -v
-	$(PYTHON) $(srcdir)/ctrl_test_runner.py -w $(abs_top_builddir) -v
+	$(srcdir)/vty_test_runner.py -w $(abs_top_builddir) -v
+	$(srcdir)/ctrl_test_runner.py -w $(abs_top_builddir) -v
 if BUILD_SMPP
-	$(PYTHON) $(srcdir)/smpp_test_runner.py -w $(abs_top_builddir) -v
+	$(srcdir)/smpp_test_runner.py -w $(abs_top_builddir) -v
 endif
 	rm -f $(top_builddir)/sms.db
 else
diff --git a/tests/ctrl_test_runner.py b/tests/ctrl_test_runner.py
old mode 100644
new mode 100755
index 05d3e30..f652a67
--- a/tests/ctrl_test_runner.py
+++ b/tests/ctrl_test_runner.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python2
 
 # (C) 2013 by Jacob Erlbeck <jerlbeck@sysmocom.de>
 # (C) 2014 by Holger Hans Peter Freyther
diff --git a/tests/smpp_test_runner.py b/tests/smpp_test_runner.py
old mode 100644
new mode 100755
index 7a3a342..f6567d9
--- a/tests/smpp_test_runner.py
+++ b/tests/smpp_test_runner.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python2
 
 # (C) 2014 by Holger Hans Peter Freyther
 # based on vty_test_runner.py:
diff --git a/tests/vty_test_runner.py b/tests/vty_test_runner.py
old mode 100644
new mode 100755
index 6d8ca6f..471ecf6
--- a/tests/vty_test_runner.py
+++ b/tests/vty_test_runner.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python2
 
 # (C) 2013 by Katerina Barone-Adesi <kat.obsc@gmail.com>
 # (C) 2013 by Holger Hans Peter Freyther