Issue #11759 has been reported by Mike Perham.

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Bug #11759: URI breaks with frozen strings
https://bugs.ruby-lang.org/issues/11759

* Author: Mike Perham
* Status: Open
* Priority: Normal
* Assignee: 
* ruby -v: 2.3.0-preview1
* Backport: 2.0.0: UNKNOWN, 2.1: UNKNOWN, 2.2: UNKNOWN
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It appears URI uses String mutation and breaks frozen string mode.

~~~
$ RUBYOPT="--enable-frozen-string-literal" bundle exec rake
/Users/mike/.rubies/ruby-2.3.0-preview1/lib/ruby/2.3.0/uri/generic.rb:1344:in `to_s': can't modify frozen String (RuntimeError)
/Users/mike/.gem/ruby/2.3.0/gems/bundler-1.10.6/lib/bundler/source/rubygems.rb:257:in `normalize_uri'
/Users/mike/.gem/ruby/2.3.0/gems/bundler-1.10.6/lib/bundler/source/rubygems.rb:198:in `add_remote'
/Users/mike/.gem/ruby/2.3.0/gems/bundler-1.10.6/lib/bundler/source/rubygems.rb:25:in `block in initialize'
/Users/mike/.gem/ruby/2.3.0/gems/bundler-1.10.6/lib/bundler/source/rubygems.rb:25:in `reverse_each'
/Users/mike/.gem/ruby/2.3.0/gems/bundler-1.10.6/lib/bundler/source/rubygems.rb:25:in `initialize'
~~~



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