// Model/Table/UsersProfilesTable.php

 class UserProfilesTable extends Table{

    public function validationDefault(Validator $validator){

        $validator  =   new Validator();

        $validator
            ->notEmpty("first_name","First name cannot be empty.")
            ->requirePresence("first_name")
            .......
            ->notEmpty("email", "Email cannot be empty.")
            ->requirePresence("email")
            ->add( "email", "email",[
                "rule" => ["email", true],
                "message" => "Enter a valid e-mail."
            ]);



        return $validator;
    }

    public function buildRules(RulesChecker $rules){

        $rules->add($rules->isUnique(['email'], 'Email should be unique'));

        return $rules;
    }

//UsersController.php

      $user =   $this->Users->patchEntity($user, $this->request->data);

      if($this->Users->save($user)){
        // Success msg
      }

      if($user->errors()){
         // This shows all the error messages except the one specified in the  buildRules for unique email.
         pr($user->errors());
      }