Misleading error message on webspace quota problems

[instantflorian]

When the webspace of a domain is completely used, neither page accessfiles can be written, nor media can be uploaded, nor modules can be installed. Also, no existing files can be changed.
So far so clear, but in that case, the error message is completely misleading, e.g. according to that, insufficient access rights would be the problem, which is actually wrong.
So in case of writing issues, there should also be a test with disk_free_space to make sure that a helpful error message is shown.