Fix behaviour when file handles a path with tilde

Two problems here
* unchecked exception handling and erroneous assumption as to why
  an exception might fire
* although the file module expands the path, when using file_args
  the unexpanded path is passed.

Expected result: ~/path/to/file should work fine
Actual result: exception is because it doesn't find file with a message
about not being able to get the selinux context
Merge pull request #1830 from willthames/fix_tilde_path_in_file

Fix behaviour when file handles a path with tilde