[rubygems/rubygems] Improve frozen mode error message

This error message is also printed when using `bundler/setup` in frozen
model, so we're not necessarily installing any gems when it happens.

This new message play nicer with all situations.

https://github.com/rubygems/rubygems/commit/6874bbacce

lib/bundler/definition.rb

@@ -364,18 +364,6 @@ module Bundler
     end
 
     def ensure_equivalent_gemfile_and_lockfile(explicit_flag = false)
-      msg = String.new
-      msg << "You are trying to install in frozen mode after changing your Gemfile.\n" \
-             "Run `bundle install` elsewhere and add the updated #{Bundler.default_lockfile.relative_path_from(SharedHelpers.pwd)} to version control.\n"
-
-      unless explicit_flag
-        suggested_command = unless Bundler.settings.locations("frozen").keys.include?(:env)
-          "bundle config set frozen false"
-        end
-        msg << "If this is a development machine, remove the #{Bundler.default_gemfile.relative_path_from(SharedHelpers.pwd)} " \
-               "freeze by running `#{suggested_command}`." if suggested_command
-      end
-
       added =   []
       deleted = []
       changed = []
@@ -405,11 +393,20 @@ module Bundler
       end
 
       reason = change_reason
-      msg << "\n\n#{reason.split(", ").map(&:capitalize).join("\n")}"
+      msg = String.new
+      msg << "#{reason.capitalize.strip}, but the lockfile can't be updated because frozen mode is set"
       msg << "\n\nYou have added to the Gemfile:\n" << added.join("\n") if added.any?
       msg << "\n\nYou have deleted from the Gemfile:\n" << deleted.join("\n") if deleted.any?
       msg << "\n\nYou have changed in the Gemfile:\n" << changed.join("\n") if changed.any?
-      msg << "\n"
+      msg << "\n\nRun `bundle install` elsewhere and add the updated #{Bundler.default_lockfile.relative_path_from(SharedHelpers.pwd)} to version control.\n"
+
+      unless explicit_flag
+        suggested_command = unless Bundler.settings.locations("frozen").keys.include?(:env)
+          "bundle config set frozen false"
+        end
+        msg << "If this is a development machine, remove the #{Bundler.default_gemfile.relative_path_from(SharedHelpers.pwd)} " \
+               "freeze by running `#{suggested_command}`." if suggested_command
+      end
 
       raise ProductionError, msg if added.any? || deleted.any? || changed.any? || !nothing_changed?
     end

spec/bundler/commands/inject_spec.rb

@@ -109,7 +109,7 @@ Usage: "bundle inject GEM VERSION"
         gem "rack-obama"
       G
       bundle "inject 'rack' '> 0'", :raise_on_error => false
-      expect(err).to match(/trying to install in frozen mode after changing/)
+      expect(err).to match(/the lockfile can't be updated because frozen mode is set/)
 
       expect(bundled_app_lock.read).not_to match(/rack-obama/)
     end

spec/bundler/commands/update_spec.rb

@@ -658,27 +658,27 @@ RSpec.describe "bundle update" do
       bundle "update", :all => true, :raise_on_error => false
 
       expect(last_command).to be_failure
-      expect(err).to match(/You are trying to install in frozen mode after changing your Gemfile/)
+      expect(err).to match(/Bundler is unlocking, but the lockfile can't be updated because frozen mode is set/)
       expect(err).to match(/freeze by running `bundle config set frozen false`./)
     end
 
     it "should fail loudly when frozen is set globally" do
       bundle "config set --global frozen 1"
       bundle "update", :all => true, :raise_on_error => false
-      expect(err).to match(/You are trying to install in frozen mode after changing your Gemfile/).
+      expect(err).to match(/Bundler is unlocking, but the lockfile can't be updated because frozen mode is set/).
         and match(/freeze by running `bundle config set frozen false`./)
     end
 
     it "should fail loudly when deployment is set globally" do
       bundle "config set --global deployment true"
       bundle "update", :all => true, :raise_on_error => false
-      expect(err).to match(/You are trying to install in frozen mode after changing your Gemfile/).
+      expect(err).to match(/Bundler is unlocking, but the lockfile can't be updated because frozen mode is set/).
         and match(/freeze by running `bundle config set frozen false`./)
     end
 
     it "should not suggest any command to unfreeze bundler if frozen is set through ENV" do
       bundle "update", :all => true, :raise_on_error => false, :env => { "BUNDLE_FROZEN" => "true" }
-      expect(err).to match(/You are trying to install in frozen mode after changing your Gemfile/)
+      expect(err).to match(/Bundler is unlocking, but the lockfile can't be updated because frozen mode is set/)
       expect(err).not_to match(/by running/)
     end
   end

spec/bundler/install/deploy_spec.rb

@@ -473,7 +473,7 @@ RSpec.describe "install in deployment or frozen mode" do
 
       run "require 'rack'", :raise_on_error => false
       expect(err).to include strip_whitespace(<<-E).strip
-The dependencies in your gemfile changed
+The dependencies in your gemfile changed, but the lockfile can't be updated because frozen mode is set (Bundler::ProductionError)
 
 You have added to the Gemfile:
 * rack (= 1.0.0)
@@ -506,7 +506,7 @@ You have deleted from the Gemfile:
       simulate_new_machine
       bundle "config set --local deployment true"
       bundle "install --verbose"
-      expect(out).not_to include("You are trying to install in frozen mode after changing your Gemfile")
+      expect(out).not_to include("but the lockfile can't be updated because frozen mode is set")
       expect(out).not_to include("You have added to the Gemfile")
       expect(out).not_to include("You have deleted from the Gemfile")
       expect(out).to include("vendor/cache/foo")

spec/bundler/install/gemfile/gemspec_spec.rb

@@ -150,7 +150,7 @@ RSpec.describe "bundle install from an existing gemspec" do
     output = bundle("install", :dir => tmp.join("foo"))
     expect(output).not_to match(/You have added to the Gemfile/)
     expect(output).not_to match(/You have deleted from the Gemfile/)
-    expect(output).not_to match(/install in frozen mode after changing/)
+    expect(output).not_to match(/the lockfile can't be updated because frozen mode is set/)
   end
 
   it "should match a lockfile without needing to re-resolve" do