Re-raise Redis connection errors

See leandromoreira#108

lib/redlock/client.rb

@@ -170,8 +170,6 @@ def lock(resource, val, ttl, allow_new_lock)
         recover_from_script_flush do
           @redis.with { |conn| conn.evalsha Scripts::LOCK_SCRIPT_SHA, keys: [resource], argv: [val, ttl, allow_new_lock] }
         end
-      rescue Redis::BaseConnectionError
-        false
       end
 
       def unlock(resource, val)

spec/client_spec.rb

@@ -242,14 +242,14 @@ def redis.with
     end
 
     context 'when a server goes away' do
-      it 'does not raise an error on connection issues' do
-        # We re-route the lock manager to a (hopefully) non-existent Redis URL.
+      it 'raises an error on connection issues' do
+        # Set lock manager to a (hopefully) non-existent Redis URL to test error
         redis_instance = lock_manager.instance_variable_get(:@servers).first
         redis_instance.instance_variable_set(:@redis, unreachable_redis)
 
         expect {
-          expect(lock_manager.lock(resource_key, ttl)).to be_falsey
-        }.to_not raise_error
+          lock_manager.lock(resource_key, ttl)
+        }.to raise_error(Redis::CannotConnectError)
       end
     end
 
@@ -259,7 +259,9 @@ def redis.with
         redis_instance = lock_manager.instance_variable_get(:@servers).first
         old_redis = redis_instance.instance_variable_get(:@redis)
         redis_instance.instance_variable_set(:@redis, unreachable_redis)
-        expect(lock_manager.lock(resource_key, ttl)).to be_falsey
+        expect {
+          lock_manager.lock(resource_key, ttl)
+        }.to raise_error(Redis::CannotConnectError)
         redis_instance.instance_variable_set(:@redis, old_redis)
         expect(lock_manager.lock(resource_key, ttl)).to be_truthy
       end