I think that something changed in neo4j-core API, making this gem incompatible :\
I'm running neo4j-core 6.1.4 and neo4j master HEAD
$ bin/rails c
/Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/neo4j-core-6.1.4/lib/neo4j-server/cypher_session.rb:9:in `<module:Server>': superclass mismatch for class CypherSession (TypeError)
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/neo4j-core-6.1.4/lib/neo4j-server/cypher_session.rb:4:in `<module:Neo4j>'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/neo4j-core-6.1.4/lib/neo4j-server/cypher_session.rb:3:in `<top (required)>'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:274:in `require'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:274:in `block in require'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:240:in `load_dependency'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:274:in `require'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/neo4j-core-6.1.4/lib/neo4j-server.rb:9:in `<top (required)>'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:274:in `require'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:274:in `block in require'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:240:in `load_dependency'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:274:in `require'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/neo4j-core-6.1.4/lib/neo4j/session.rb:102:in `open'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/bundler/gems/neo4j-db5546e1b0ec/lib/neo4j/railtie.rb:106:in `block in open_neo4j_session'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/bundler/gems/neo4j-db5546e1b0ec/lib/neo4j/railtie.rb:119:in `block in wait_for_value'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/2.3.0/timeout.rb:91:in `block in timeout'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/2.3.0/timeout.rb:33:in `block in catch'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/2.3.0/timeout.rb:33:in `catch'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/2.3.0/timeout.rb:33:in `catch'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/2.3.0/timeout.rb:106:in `timeout'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/bundler/gems/neo4j-db5546e1b0ec/lib/neo4j/railtie.rb:116:in `wait_for_value'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/railties-4.2.6/lib/rails/railtie.rb:194:in `public_send'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/railties-4.2.6/lib/rails/railtie.rb:194:in `method_missing'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/bundler/gems/neo4j-db5546e1b0ec/lib/neo4j/railtie.rb:102:in `open_neo4j_session'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/bundler/gems/neo4j-db5546e1b0ec/lib/neo4j/railtie.rb:159:in `block (2 levels) in <class:Railtie>'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/bundler/gems/neo4j-db5546e1b0ec/lib/neo4j/railtie.rb:158:in `each'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/bundler/gems/neo4j-db5546e1b0ec/lib/neo4j/railtie.rb:158:in `block in <class:Railtie>'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/railties-4.2.6/lib/rails/initializable.rb:30:in `instance_exec'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/railties-4.2.6/lib/rails/initializable.rb:30:in `run'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/railties-4.2.6/lib/rails/initializable.rb:55:in `block in run_initializers'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/2.3.0/tsort.rb:228:in `block in tsort_each'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/2.3.0/tsort.rb:350:in `block (2 levels) in each_strongly_connected_component'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/2.3.0/tsort.rb:431:in `each_strongly_connected_component_from'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/2.3.0/tsort.rb:349:in `block in each_strongly_connected_component'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/2.3.0/tsort.rb:347:in `each'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/2.3.0/tsort.rb:347:in `call'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/2.3.0/tsort.rb:347:in `each_strongly_connected_component'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/2.3.0/tsort.rb:226:in `tsort_each'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/2.3.0/tsort.rb:205:in `tsort_each'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/railties-4.2.6/lib/rails/initializable.rb:54:in `run_initializers'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/railties-4.2.6/lib/rails/application.rb:352:in `initialize!'
from /Users/progm/lavoro/foldesk/config/environment.rb:5:in `<top (required)>'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:274:in `require'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:274:in `block in require'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:240:in `load_dependency'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/activesupport-4.2.6/lib/active_support/dependencies.rb:274:in `require'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/railties-4.2.6/lib/rails/application.rb:328:in `require_environment!'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/railties-4.2.6/lib/rails/commands/commands_tasks.rb:142:in `require_application_and_environment!'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/railties-4.2.6/lib/rails/commands/commands_tasks.rb:67:in `console'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/railties-4.2.6/lib/rails/commands/commands_tasks.rb:39:in `run_command!'
from /Users/progm/.rbenv/versions/2.3.1/lib/ruby/gems/2.3.0/gems/railties-4.2.6/lib/rails/commands.rb:17:in `<top (required)>'
from bin/rails:4:in `require'
from bin/rails:4:in `<main>'
I think that something changed in neo4j-core API, making this gem incompatible :\
I'm running neo4j-core 6.1.4 and neo4j master HEAD
@cheerfulstoic @subvertallchris