The docs state that you can use an alternative syntax to define the target FTP server and its configuration:

'example':
  skip: false
  scheme: ftp
  user: example
  password: password
  host: example.com
  port: 21
  path: /path/to/installation

However, at line 100 in your code you have

uri = URI.parse(uri)

and then later

options['path']     = uri.path     if uri.path

It seems that the URI.parse() method parses the 'example' as path, which is why when trying to connect the FTP, I get this error:

put: CWD /example
get: 550 Can't change directory to /example: No such file or directory

Since the uri.path seems to be defined (as parsed), then this line

ftp.chdir(options['path'].empty? ? options['chdir'] : '/' + options['path'])

tries to change the working directory to 'example' instead of the '/path/to/installation' path.

Am I missing something?