Refactor check and raise failure

- Use `cover?` which is much faster than `include?`
- Use a guard clause to improve readability
- Add a spec

```
Comparison (IPS):
              cover?:  4483987.3 i/s
            include?:  2890227.4 i/s - 1.55x  (± 0.00) slower
```

lib/sharepoint/client.rb

@@ -533,9 +533,9 @@ def last_location_header(ethon)
     end
 
     def check_and_raise_failure(ethon)
-      unless (200..299).include? ethon.response_code
-        raise "Request failed, received #{ethon.response_code}:\n#{ethon.url}\n#{ethon.response_body}"
-      end
+      return if (200..299).cover? ethon.response_code
+
+      raise "Request failed, received #{ethon.response_code}:\n#{ethon.url}\n#{ethon.response_body}"
     end
 
     def prepare_metadata(metadata, type)

spec/lib/sharepoint/client_methods_spec.rb

@@ -253,7 +253,7 @@
   end
 
   describe '#search' do
-    subject { client.search(options) }
+    subject(:search) { client.search(options) }
 
     before { mock_responses('search_modified_documents.json') }
 
@@ -267,6 +267,18 @@
     end
 
     it { is_expected.not_to be_empty }
+
+    context 'when request fails' do
+      before do
+        allow_any_instance_of(Ethon::Easy)
+          .to receive(:response_code)
+          .and_return(401)
+      end
+
+      it 'raises an error' do
+        expect { search }.to raise_error(/\ARequest failed, received 401.+/)
+      end
+    end
   end
 
   describe '#download' do