Catching known errors when opening/closing files

[gohar94]

On Windows, when opening a file which is held by another process, open call throws an exception (which is expected) - putting that in try/except.

On Linux, when closing a file that might have been closed by another process, unlink call throws an exception (which is expecting) - putting that in try/except.

[Cologler]

On my windows 10 PC, open a locked file does not raises any errors:

It raises a PermissionError only if I try to write some data into the locked file and flush it.

[yagelsyf]

Good change that I want to add too.
In rare cases that happen from time to time, its happen.

[Cologler]

I explained why this wouldn't work in #7 (comment).