updated for version 7.3.957
Problem:    Python does not have a "do" command like Perl or Lua.
Solution:   Add the ":py3do" command. (Lilydjwg)
diff --git a/src/ex_cmds.h b/src/ex_cmds.h
index b02b9f6..b9ad364 100644
--- a/src/ex_cmds.h
+++ b/src/ex_cmds.h
@@ -743,6 +743,8 @@
 			RANGE|FILE1|NEEDARG|CMDWIN),
 EX(CMD_py3,		"py3",		ex_py3,
 			RANGE|EXTRA|NEEDARG|CMDWIN),
+EX(CMD_py3do,		"py3do",	ex_py3do,
+			RANGE|DFLALL|EXTRA|NEEDARG|CMDWIN),
 EX(CMD_python3,		"python3",	ex_py3,
 			RANGE|EXTRA|NEEDARG|CMDWIN),
 EX(CMD_py3file,		"py3file",	ex_py3file,