Rescue Faraday::TimeoutError

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

@@ -5,6 +5,8 @@
 
 module OAuth2
   ConnectionError = Class.new(Faraday::ConnectionFailed)
+  TimeoutError = Class.new(Faraday::TimeoutError)
+
   # The OAuth2::Client class
   class Client # rubocop:disable Metrics/ClassLength
     RESERVED_PARAM_KEYS = %w[headers parse].freeze
@@ -115,6 +117,8 @@ def request(verb, url, opts = {})
         end
       rescue Faraday::ConnectionFailed => e
         raise ConnectionError, e
+      rescue Faraday::TimeoutError => e
+        raise TimeoutError, e
       end
 
       response = Response.new(response, parse: opts[:parse])

spec/oauth2/client_spec.rb

@@ -431,17 +431,35 @@
     context 'when errors are raised by Faraday' do
       let(:connection) { instance_double(Faraday::Connection, build_url: double) }
 
-      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
 
-        expect { subject.request(:get, '/redirect') }.to raise_error do |e|
-          expect(e.class).to eq(OAuth2::ConnectionError)
-          expect(e.message).to eq('fail')
+      shared_examples 'failed connection handler' do
+        it 'rescues the exception' do
+          expect { subject.request(:get, '/redirect') }.to raise_error do |e|
+            expect(e.class).to eq(expected_exception)
+            expect(e.message).to eq(faraday_exception.message)
+          end
         end
       end
+
+      context 'with Faraday::ConnectionFailed' do
+        let(:faraday_exception) { Faraday::ConnectionFailed.new('fail') }
+        let(:expected_exception) { OAuth2::ConnectionError }
+
+        it_behaves_like 'failed connection handler'
+      end
+
+      context 'with Faraday::TimeoutError' do
+        let(:faraday_exception) { Faraday::TimeoutError.new('timeout') }
+        let(:expected_exception) { OAuth2::TimeoutError }
+
+        it_behaves_like 'failed connection handler'
+      end
     end
   end