[snap] failure to open templates from startcenter

[Olivier Tilloy]

(initially reported here: https://forum.snapcraft.io/t/libreoffice-snap-missing-features-and-known-bugs/3920/2)

When trying to open any template from the startcenter, the following error is displayed in a message box:

    General input/output error while accessing /snap/libreoffice/47/lib/libreoffice/share/template/common/presnt/Blueprint_Plans.otp.

However the same templates can be opened and used from the individual apps, e.g. from impress for that Blueprint_Plans template.

[Olivier Tilloy (osomon)]

Stracing the app reveals what the problem is:

12442 open("/snap/libreoffice/47/lib/libreoffice/share/template/common/presnt/Blueprint_Plans.otp", O_RDWR) = -1 EROFS (Read-only file system)

the app is trying to open the template file in read/write mode, but it's in a read-only location.

[Olivier Tilloy (osomon)]

The same operation (opening a template file) succeeds with libreoffice installed as a deb, and the template is read-only too. The major difference between the two is that in the case of the deb the error code when trying to open the file in write mode is EACCES, whereas for the snap it's EROFS. I guess libreoffice handles those two situations differently.