def make_credentials(inline_user, inline_password)
      user = inline_user || @default_user
      user = nil if user && user.empty?
      password = (inline_password || @default_password)
      password = nil if password && password.empty?
      [user, password]
    end
def make_credentials(inline_user, inline_password)
      user = inline_user || @default_user
      user = nil if user && user.empty?
      password = (inline_password || @default_password)
      password = nil if password && password.empty?
      [user, password]
    end
Merge the inline user/pass with the default user/pass, giving
 precedence to inline.