Add python3 check

Author: tuhaihe

configure

@@ -744,6 +744,7 @@ with_gssapi
 with_pythonsrc_ext
 PIP3
 CURL
+PYTHON3
 with_python
 with_perl
 with_tcl
@@ -9896,6 +9897,50 @@ $as_echo "$with_pythonsrc_ext" >&6; }
 
 # Check for required dependencies when pythonsrc-ext is enabled
 if test "$with_pythonsrc_ext" = yes; then
+  # Extract the first word of "python3", so it can be a program name with args.
+set dummy python3; ac_word=$2
+{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5
+$as_echo_n "checking for $ac_word... " >&6; }
+if ${ac_cv_path_PYTHON3+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+  case $PYTHON3 in
+  [\\/]* | ?:[\\/]*)
+  ac_cv_path_PYTHON3="$PYTHON3" # Let the user override the test with a path.
+  ;;
+  *)
+  as_save_IFS=$IFS; IFS=$PATH_SEPARATOR
+for as_dir in $PATH
+do
+  IFS=$as_save_IFS
+  test -z "$as_dir" && as_dir=.
+    for ac_exec_ext in '' $ac_executable_extensions; do
+  if as_fn_executable_p "$as_dir/$ac_word$ac_exec_ext"; then
+    ac_cv_path_PYTHON3="$as_dir/$ac_word$ac_exec_ext"
+    $as_echo "$as_me:${as_lineno-$LINENO}: found $as_dir/$ac_word$ac_exec_ext" >&5
+    break 2
+  fi
+done
+  done
+IFS=$as_save_IFS
+
+  ;;
+esac
+fi
+PYTHON3=$ac_cv_path_PYTHON3
+if test -n "$PYTHON3"; then
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: $PYTHON3" >&5
+$as_echo "$PYTHON3" >&6; }
+else
+  { $as_echo "$as_me:${as_lineno-$LINENO}: result: no" >&5
+$as_echo "no" >&6; }
+fi
+
+
+  if test -z "$PYTHON3"; then
+    as_fn_error $? "python3 is required for --with-pythonsrc-ext but was not found" "$LINENO" 5
+  fi
+
   # Extract the first word of "curl", so it can be a program name with args.
 set dummy curl; ac_word=$2
 { $as_echo "$as_me:${as_lineno-$LINENO}: checking for $ac_word" >&5

configure.ac

@@ -1080,6 +1080,11 @@ AC_MSG_RESULT([$with_pythonsrc_ext])
 
 # Check for required dependencies when pythonsrc-ext is enabled
 if test "$with_pythonsrc_ext" = yes; then
+  AC_PATH_PROG([PYTHON3], [python3])
+  if test -z "$PYTHON3"; then
+    AC_MSG_ERROR([python3 is required for --with-pythonsrc-ext but was not found])
+  fi
+
   AC_PATH_PROG([CURL], [curl])
   if test -z "$CURL"; then
     AC_MSG_ERROR([curl is required for --with-pythonsrc-ext but was not found])