Rescue Faraday::ServerErrror

If Faraday hits a timeout, it will raise a `Faraday::TimeoutError`.
Re-raise this as an `OAuth2::ConnectionError`, reusing the logic in
oauth-xx#549.

This came up in omniauth/omniauth-oauth2#129.

lib/oauth2/client.rb

@@ -113,7 +113,7 @@ def request(verb, url, opts = {})
           req.params.update(opts[:params]) if opts[:params]
           yield(req) if block_given?
         end
-      rescue Faraday::ConnectionFailed => e
+      rescue Faraday::ConnectionFailed, Faraday::ServerError => e
         raise ConnectionError, e
       end
 

spec/oauth2/client_spec.rb

@@ -430,16 +430,32 @@
 
     context 'when errors are raised by Faraday' do
       let(:connection) { instance_double(Faraday::Connection, build_url: double) }
+      let(:faraday_exception) { Faraday::ConnectionFailed.new('fail') }
 
-      it 'rescues Faraday::ConnectionFailed' do
+      before do
         allow(connection).to(
-          receive(:run_request).and_raise(Faraday::ConnectionFailed.new('fail'))
+          receive(:run_request).and_raise(faraday_exception)
         )
         allow(subject).to receive(:connection).and_return(connection) # rubocop:disable RSpec/SubjectStub
+      end
+
+      context 'with Faraday::ConnectionFailed' do
+        it 'rescues the exception' do
+          expect { subject.request(:get, '/redirect') }.to raise_error do |e|
+            expect(e.class).to eq(OAuth2::ConnectionError)
+            expect(e.message).to eq('fail')
+          end
+        end
+      end
 
-        expect { subject.request(:get, '/redirect') }.to raise_error do |e|
-          expect(e.class).to eq(OAuth2::ConnectionError)
-          expect(e.message).to eq('fail')
+      context 'with Faraday::TimeoutError' do
+        let(:faraday_exception) { Faraday::TimeoutError.new('timeout') }
+
+        it 'rescues the exception' do
+          expect { subject.request(:get, '/redirect') }.to raise_error do |e|
+            expect(e.class).to eq(OAuth2::ConnectionError)
+            expect(e.message).to eq('timeout')
+          end
         end
       end
     end