Refactor sync_environment methods

* Add delete_environment method
* Change return value to allow raising an exception

spec/lib/runner/strategy/poseidon_spec.rb

@@ -141,11 +141,11 @@ describe Runner::Strategy::Poseidon do
     end
 
     shared_examples 'returns false when the api request failed' do |status|
-      it "returns false on status #{status}" do
+      it "raises an exception on status #{status}" do
         faraday_connection = instance_double 'Faraday::Connection'
         allow(described_class).to receive(:http_connection).and_return(faraday_connection)
         allow(faraday_connection).to receive(:put).and_return(Faraday::Response.new(status: status))
-        expect(action.call).to be_falsey
+        expect { action.call }.to raise_exception Runner::Error::UnexpectedResponse
       end
     end
 
@@ -157,11 +157,11 @@ describe Runner::Strategy::Poseidon do
       include_examples 'returns false when the api request failed', status
     end
 
-    it 'returns false if Faraday raises an error' do
+    it 'raises an exception if Faraday raises an error' do
       faraday_connection = instance_double 'Faraday::Connection'
       allow(described_class).to receive(:http_connection).and_return(faraday_connection)
       allow(faraday_connection).to receive(:put).and_raise(Faraday::TimeoutError)
-      expect(action.call).to be_falsey
+      expect { action.call }.to raise_exception Runner::Error::FaradayError
     end
   end