Guido Gunther authored Jan 19, 2021 and Zander Brown committed Jan 19, 2021

gtk_css_provider_load_from_resource is simpler and prints
enough error information even without connecting to "parsing-error":

  (phosh:157249): Gtk-WARNING **: 17:18:36.290: Theme parsing error: <broken file>:1:0: Failed to import: The resource at “/resource:/sm/puri/phosh/style.cs” does not exist

Prompted by calls!235

Signed-off-by: Guido Günther <guido.gunther@puri.sm>