gpg: WARNING: unsafe permissions on configuration file `/home/david/.gnupg/gpg.conf'
gpg: WARNING: unsafe enclosing directory permissions on configuration file `/home/david/.gnupg/gpg.conf'
gpg: external program calls are disabled due to unsafe options file permissions
gpg: keyserver communications error: general error
gpg: keyserver receive failed: general error
What does it mean and how to fix?