If you are using watches, you need to take the following steps:
Before editing a file, issue the command cvs edit:
$ cvs edit hello.py $
Notification is then sent to all people who have an edit watch set.
When you commit the file, notification will be sent to all watchers.
If you decide you want to abort your changes, you can issue the cvs unedit command. Note that in doing so your file will be reverted back to the state of the last commit. Example:
$ cvs unedit hello.py hello.py has been modified; revert changes? y $
Notification will be sent to all of those with an unedit watch.