What Causes the Error?
Both of these methods take two arguments, a filename and a format. The format should be either the symbol :yaml or :cookiestxt. The :yaml argument obviously instructs Mechanize to save the cookie jar in YAML format, and :cookiestxt to save in Mozilla-compatible cookies.txt format.
If the format argument is anything but these two symbols, it will raise the "Unknown cookie jar file format" error.
For instance, this will cause the error to be raised.
agent.cookie_jar.save_as('some_file', :unknownformat)How do I Fix the Error?
Pass either :yaml or :cookiestxt as the second parameter to Mechanize::CookieJar#save_as or Mechanize::CookieJar#load. Alternatively, pass no second argument to the methods, as the default for the second argument is :yaml.
The following are valid ways to call Mechanize::CookieJar#save_as or Mechanize::CookieJar#load.
agent.cookie_jar.save_as('cookies.yaml')agent.cookie_jar.save_as('cookies.yaml', :yaml)agent.cookie_jar.save_as('cookies.txt', :cookiestxt)agent.cookie_jar.load('cookies.yaml')agent.cookie_jar.load('cookies.yaml', :yaml)agent.cookie_jar.load('cookies.txt', :cookiestxt)