Fix typo for python 3 support

This change simply enables the existing check in configure.ac to function as intended.

Signed-off-by: Christopher Friedt <chrisfriedt@gmail.com>
diff --git a/configure.ac b/configure.ac
index 64283a8..f3f88a7 100755
--- a/configure.ac
+++ b/configure.ac
@@ -325,7 +325,7 @@
 have_py3="no"
 AX_THRIFT_LIB(py3, [Py3], yes)
 if test "$with_py3" = "yes"; then
-  if $PYTHON --version 2>&1 | grep -q "Python 2"; then
+  if $PYTHON --version 2>&1 | grep -q "Python 3"; then
     AC_PATH_PROGS([PYTHON3], [python3 python3.7 python37 python3.6 python36 python3.5 python35 python3.4 python34])
     if test -n "$PYTHON3"; then
       have_py3="yes"