Update shoulda-matchers to version 4.0.0

We use a custom validation error message for the kiwi repository model. With the
new gem release the error message shoulda matchers would expect wasn't matching
our custom message and the test failed.
To solve this we explicitly set the validation message in the test.

Co-authored-by: Björn Geuken <bgeuken@suse.de>

src/api/Gemfile

@@ -132,7 +132,7 @@ group :test do
   # for mocking and stubbing
   gem 'mocha', '> 0.13.0', require: false
   # for testing common Rails functionality with simple one-liners
-  gem 'shoulda-matchers', '~> 3.1'
+  gem 'shoulda-matchers', '~> 4.0'
   # assigns has been extracted to a gem
   gem 'rails-controller-testing'
   # To generate random data

src/api/Gemfile.lock

@@ -388,8 +388,8 @@ GEM
       childprocess (~> 0.5)
       rubyzip (~> 1.2, >= 1.2.2)
     sexp_processor (4.11.0)
-    shoulda-matchers (3.1.3)
-      activesupport (>= 4.0.0)
+    shoulda-matchers (4.0.0)
+      activesupport (>= 4.2.0)
     simplecov (0.16.1)
       docile (~> 1.1)
       json (>= 1.8, < 3)
@@ -534,7 +534,7 @@ DEPENDENCIES
   sanitize
   sassc-rails
   selenium-webdriver
-  shoulda-matchers (~> 3.1)
+  shoulda-matchers (~> 4.0)
   simplecov
   single_test
   sprite-factory (>= 1.5.2)

src/api/spec/models/kiwi/repository_spec.rb

@@ -111,7 +111,10 @@
 
     # We specific the context of the inclusion validation because of a bug in shoulda_matcher.
     # Remove `.on(:save)` when it's solved.
-    it { is_expected.to validate_inclusion_of(:repo_type).in_array(Kiwi::Repository::REPO_TYPES).on(:save) }
+    it do
+      expect(subject).to validate_inclusion_of(:repo_type).in_array(Kiwi::Repository::REPO_TYPES).on(:save)
+                                                          .with_message(/is not included in the list/)
+    end
     it do
       expect(subject).to validate_numericality_of(:priority).is_greater_than_or_equal_to(0).is_less_than(100)
                                                             .with_message(/must be between 0 and 99/)