This method is only available on newer versions.
The first available version (v2_6_3) is shown here.
allow_missing?(dependency)
public
(see Bundler::Molinillo::SpecificationProvider#allow_missing?)
# File lib/bundler/vendor/molinillo/lib/molinillo/delegates/specification_provider.rb, line 58
def allow_missing?(dependency)
with_no_such_dependency_error_handling do
specification_provider.allow_missing?(dependency)
end
end