Split a reusable test base class and use self.username variable.

Also don't set username as reference on person, this is no longer needed
since ERP5 Login.

This reverts commit 750e2bfc.

This looks wrong to me, we don't send errors to users like this. And if we
really want to do, we should ignore error like this but use CMFActivity
error call back.

For now, let's revert.

erp5_property_sheets: Buce uses ad-hoc Manufacturing Orders without transformation and allows empty lines

Purchase Orders are created in draft state and must be confirmed by psa user

* The issue was that when a lot of change management had the same effective date, sometimes, fixing the consistency of the change management led to invalidating the one that was the latest one.
* XXX CLN: Maybe some verification on the version would have been better.

* Also move the variable definition before they are used.

1. add copy&paste excel
2. show message when copy
3. update total when value change