Can't update to a branch where a subrepo asks for a password.

I have a case where I'm using HG Flow and I have default and develop branch. As I work a lot in the develop branch I didn't merge the default for a long time.

In default, there is a subrepo which origin is in my own server (it's a private repo) and it requires login/password to access to. As usual if I clone that repository alone, or the parent repo, SourceTree will ask for the password.

However, if removed that subrepo in the develop branch. Now, I want to merge the develop branch into the default branch.
So I first update to the default branch.
But on update there is an error saying that there is a subrepo that needs login/password. and that the operation was done with failure.
Unfortunately I'm not exactly sure

What I expected was the usual login/password window to spawn.

(To continue my work I used TortoiseHG to do the operation, it just asked the subrepos passwords; I guess it's just a prompt call missing in SourceTree)