Undefined method log for Selenium::WebDriver::Remote::W3C::Bridge

I believe that when WEBrick has trouble bringing up your Rails application, the WEBrick component that is supposed to print you a pretty error message has a bug and sometimes fails with this message:

"undefined method `bytesize' for #<Array>"...

So you're getting an error like this:

undefined method `activate_bin_path' for Gem:Module (NoMethodError)

Here is what happened:

• You installed a recent version of Rubygems
• You installed some gems that install a binary (like `bun...

On recent/fresh installations of Ruby 1.8.7 you may encounter this error why calling any bundled binary (or just bundle exec):

/home/arne/.rvm/gems/ruby-1.8.7-p374@global/gems/rubygems-bundler-1.4.2/lib/rubygems-bundler/noexec.rb:75:in ...

I got this error when running Rails 2.3 tests for Rails LTS. More stacktrace:

NoMethodError: undefined method `cache' for Gem:Module
    /vagrant/rails-2-3-lts-repository/railties/lib/rails_generator/lookup.rb:212:in `e...

You are probably using Ruby 1.8.7 with a too recent versions of Rubygems.

Downgrade your Rubygems to the latest version that works with 1.8.7.

See also

• [Fix Rubygems warning: Gem.source_index is deprecated, use Specifica...

In newer passenger versions the output of passenger -v has changed. capistrano-passenger tries to parse the version and now causes the error undefined method '[]' for nil:NilClass. To fix this you only need to upgrade the `capistrano-passeng...

to_file has been removed in Paperclip 3.0.1.

Instead of using File to access Paperclip storage objects (like this: File.read(file.to_file.path)) you can use

Paperclip.io_adapters.fo...

Phillip Koebbe from Ruby on Rails suggested inserting following code between the "bootstrap" and "initialize" sections of enviroment.rb. This hack fixes the problem.

if Gem::VERSION >= "1.3.6"
  module Rails
    class GemDependency

...

Upgrade the offending gem. If you cannot or don't want to upgrade, lock rake to 0.8.7.

You might have a table without a primary key set in MySQL.

You can fix this by adding a primary key index to the guilty MySQL table, or by setting self.primary_key = "id" in your class definition.

Related, but different issue: [Rails 2 does no...