Append chardet to dependencies.

Signed-off-by: Kouhei Maeda <mkouhei@palmtb.net>
Fixed process when fail to siging.

Signed-off-by: Kouhei Maeda <mkouhei@palmtb.net>
Support not default keyring and keyid.

Signed-off-by: Kouhei Maeda <mkouhei@palmtb.net>
Added unit test and dummy GPG keyring, dummy debian package.

Signed-off-by: Kouhei Maeda <mkouhei@palmtb.net>