Pinta incorrectly thinks file already exists if it lacks read permissions for folder in save-as dialog

[Christian Ridderborg]

Reproduction steps:
1. Open pinta as regular user that do not have read access to '/root'
2. Save-as to name: '/root/test.png'
3. Pinta reports:
"A file named "test.png" already exists. Do you want to replace it?
The file already exists in "/". Replacing it will overwrite its contents"

This message is incorrect as the file '/root/test.png' does not exist.
If the user tries to manually go to the folder first, they are correctly informed that Pinta cannot read the folder because it does not have permission to do so.

If the user goes ahead tries to save anyway and the folder is also write protected it triggers bug:
https://bugs.launchpad.net/pinta/+bug/1715150

[grofaty (grofaty)]

I tested this problem in Pinta Ubuntu's Daily PPA 1.7+r1134-202008032046~ubuntu18.04.1 I can confirm the behaviour.

Because exception explains it is permission problem and average user will not save files at "strange locations" I think we can post pone this bug after 1.7 release.