heroku/heroku — pull request #1234 by deafbybeheading (2014-10-17 17:41:36+00:00)
Title: Prompt for 2fa on stderr instead of stdout

This means that a 2fa prompt is still visible if, e.g., one is piping the result of a heroku command which requires 2fa into another command:

Before this patch:

```console
maciek@gamera:~/code/heroku$ bin/heroku config -a db-corral | grep foo
# hangs indefinitely after the above; it does actually work if i just feed it
# my 2fa code blind, but i have to know to do that
ccccccdlnndrcidhrtgligivrvvlfetgdnkukhrrhfef
foo: 4
test: foo
maciek@gamera:~/code/heroku$
```

After this patch:

```console
maciek@gamera:~/code/heroku$ bin/heroku config -a db-corral | grep foo
# now shows prompt before waiting for 2fa code
Two-factor code: ccccccdlnndrtrnebkkclicdbbfcrhiideekjgncetun
foo: 4
test: foo
maciek@gamera:~/code/heroku$
```