ERPNext Update process problem with Help files

In the update process did not find the help files:

Migrating erpnext.vm
Updating DocTypes for frappe : [========================================]
Updating DocTypes for erpnext : [========================================]
Syncing help database…
/home/frappe/frappe-bench/apps/frappe/frappe/build.py:106: UserWarning: Source /home/frappe/frappe-bench/apps/erpnext_demo/erpnext_demo/docs does not exists.
warnings.warn(‘Source {source} does not exists.’.format(source = source))

VM VIRTUALBOX: 5.1.30
Installed Apps

ERPNext: v9.1.6 (master)

Frappe Framework: v9.1.8 (master)

Did this break your update? its just a warning. You have erpnext-demo app installed, its now a part of the core.
Thanks

@Ranjith

No it is not breaks the update.

I use the VM from 2017 January, and
updated last week, there was no WARN,
updated today there is WARN.

Yes I have installed together with demo data.

It may help a git pull, git fetch?

Guess you can ignore the warning.