configure.ac: migrate from python2 to python3

Fortunatelly we don't have any python2 specific code, so just bump.

Change-Id: Ib293c60cf66000b3e2520f7a02f39c4baa1c5ce9
diff --git a/configure.ac b/configure.ac
index 568584d..3effcde 100644
--- a/configure.ac
+++ b/configure.ac
@@ -110,9 +110,9 @@
 				[Include the VTY/CTRL tests in make check [default=no]]),
 		[enable_ext_tests="$enableval"],[enable_ext_tests="no"])
 if test "x$enable_ext_tests" = "xyes" ; then
-	AC_CHECK_PROG(PYTHON2_AVAIL,python2,yes)
-	 if test "x$PYTHON2_AVAIL" != "xyes" ; then
-		AC_MSG_ERROR([Please install python2 to run the VTY/CTRL tests.])
+	AC_CHECK_PROG(PYTHON3_AVAIL,python3,yes)
+	 if test "x$PYTHON3_AVAIL" != "xyes" ; then
+		AC_MSG_ERROR([Please install python3 to run the VTY/CTRL tests.])
 	fi
 	AC_CHECK_PROG(OSMOTESTEXT_CHECK,osmotestvty.py,yes)
 	 if test "x$OSMOTESTEXT_CHECK" != "xyes" ; then
diff --git a/osmoappdesc.py b/osmoappdesc.py
index 485a83b..56df5bc 100644
--- a/osmoappdesc.py
+++ b/osmoappdesc.py
@@ -1,4 +1,4 @@
-#!/usr/bin/env python
+#!/usr/bin/env python3
 
 app_configs = {
     "osmo-e1-recorder": ["doc/examples/osmo-e1-recorder.cfg"]