(System)FileSystem::source Throws FileNotFoundException For Permissions Issues

[saidooubella]

I am aware of this issue since it is a JDK problem and it exists as far as I know only on the JVM (I tested the MacOSArm64 target as well and It doesn't have this problem).
With this inconsistency you can't tell wether the file is not found or the issue with the permissions without doing some nasty hacks.

To replicate this problem try calling SystemFileSystem::source with an existing file with no reading permissions and inspect the class of the thrown error and repeat the same thing with an invalid path.

[fzhinkin]

@saidooubella thanks for pointing to the issue!

FileInputStream's open always throws FileNotFoundException with a message consisting of a file path and a reason inferred from the errno.

I don't really like the idea of parsing an exception message to decide which exact exception to throw. Perhaps, we should remove explicit references to FileNotFoundException from KDoc and mention generic IOException only.