Improved error reporting when ogr cannot open a file for read access would improve overall user experience.
For example a rare case where this would be useful is when using ogrinfo to query a file where the user does not have read permissions.
If the user does not have read permissions on a dataset ogrinfo currently only returns:
FAILURE: Unable to open datasource '/path/to/fn.shp' with the following drivers
...
If the problem is read permission a more explicit error would be useful.
This is a potential use case for PostGIS users when running as the postgres user to load data into a postgres database. If they attempt to call ogrinfo on a file and their postgres user does not have read permissions a more explicit error would remind them of the problem.
This is a very minor issue but would improve the ogr utility.
