#37 changed the code which finds the select2 input from using first to using find. Unfortunately Capybara chokes when it can't find a unique element with find - which happens when you have more than one select2 element in the page:
Failure/Error: fill_event_fields_with_valid_data Capybara::Ambiguous: Ambiguous match, found 2 elements matching css ".select2-container"
I don't really understand enough about the issue that #37 fixes to know what the solution should be.
(cc @machisuji)