curl command line instructions will fail when the private key is encrypted with a password

The gpg (v. 2) client uses a dialog box to prompt for private key passwords. The curl command (generated by the Keybase.io web interface) executes gpg to sign some JSON and pass it back to the server, so (I assume) the server can verify the signature with the public key stored there. This curl command does not work when gpg must prompt the user for a password with a dialog box.

The workaround is to extract the JSON from the curl command, manually create the signature with gpg, and paste the signature back into the curl command, replacing the `echo [...] | gpg [...]` command with the signature contents.

Start with the curl command generated by the Keybase.io web interface and the `echo [...] | gpg [...]` portion described in the report. Reproduce the failure with gpg v2 and an encrypted private key, then verify that the generated command can complete without relying on a dialog-box password prompt.

Written by the indexing model from the issue text.