Allow explicit not relative paths to import content

When importing content we use explicit paths, not relative ones. 

When the test suite runs, it passes in a base path (spec/fixtures). Using '.' for the base path didn't break the test suite, but did break the import on live. Change it to an empty string.

Also provide the error message in the output to ease diagnosis in future when files aren't able to be imported (to show the full path to the file it's attempting to import).