Dear Maintainer,

I cannot sign data using my gpg key. I'm not sure how to proceed with
diagnosing this error.

```
$ echo "test" | gpg --verbose --clearsign
gpg: using pgp trust model
gpg: using subkey E90E5D6448C2C663 instead of primary key 0F8D1FA50FC4B4EE
gpg: writing to stdout
-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA256

test
gpg: pinentry launched (5910 gnome3 1.1.0 /dev/pts/0 xterm-256color :0)
gpg: signing failed: No data callback in IPC
gpg: [stdin]: clear-sign failed: No data callback in IPC

```

I have set my GPG_TTY environment variable: `export GPG_TTY=$(tty)`