[entropy.client] _setup_differential_download: drop access() usage
[entropy.client] __approve_edelta: drop access() usage
[entropy.client] _match_checksum: drop access() usage
[entropy.client] _remove_content_from_system_loop: drop access() usage
[entropy.tools] istextfile: catch OSError and IOError exceptions
[entropy.client] _handle_config_protect: drop access() usage
[entropy.client] __generate_fetch_metadata: drop access() usage