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bundle install fails if you use Ruby < 2.5 and bundler < 1.15.2.

Gem::InstallError: stringio requires Ruby version >= 2.5.
An error occurred while installing stringio (0.1.3), and Bundler
cannot continue.
Make sure that `gem install stringio -v '0.1.3'` succeeds before bundling.

In Gemfile:
  csv was resolved to 3.1.6, which depends on
    stringio

This is because Bundler attempts to install csv 3.1.6 that does not support Ruby 2.4. csv 3.1.6 itself supports Ruby 2.3 or later, however, a dependant stringio 0.1.3 requires Ruby 2.5 or higher.

It can be fixed with the following patch.

Index: Gemfile
===================================================================
--- Gemfile    (revision 19912)
+++ Gemfile    (working copy)
@@ -12,7 +12,7 @@
 gem "roadie-rails", (RUBY_VERSION < "2.5" ? "~> 1.3.0" : "~> 2.1.0")
 gem "mimemagic" 
 gem "mail", "~> 2.7.1" 
-gem "csv", "~> 3.1.1" 
+gem 'csv', (RUBY_VERSION < '2.5' ? ['>= 3.1.1', '< 3.1.5'] : '~> 3.1.1')
 gem "nokogiri", "~> 1.10.0" 
 gem 'i18n', '~> 1.8.2'
 gem "rbpdf", "~> 1.20.0"