Magento2 have used little bit different type of exception handling for creating thrown exception and check the exception type.

Before thrown the exception and check you have to check Magento in build excpetion type

**Here the list exception type from [Magento/Framework/Exception][1]**

    AbstractAggregateException.php	
    AlreadyExistsException.php	
    AuthenticationException.php
    AuthorizationException.php	
    ConfigurationMismatchException.php
    CouldNotDeleteException.php
    CouldNotSaveException.php
    CronException.php
    EmailNotConfirmedException.php
    FileSystemException.php
    InputException.php
    IntegrationException.php
    InvalidEmailOrPasswordException.php
    LocalizedException.php
    MailException.php
    NoSuchEntityException.php
    NotFoundException.php
    PaymentException.php
    RemoteServiceUnavailableException.php
    RuntimeException.php
    SecurityViolationException.php
    SerializationException.php
    SessionException.php
    StateException.php
    TemporaryStateExceptionInterface.php
    ValidatorException.php


This exceptions type are used at Magento2.

How Magento define the exception.

**Define Error type**
Suppose, you want show throw exception of already to exist then 

Then you throw error like

   

     if (Condition) {
            throw new \Magento\Framework\Exception\AlreadyExistsException(
                __('This record already exits')
            );
        }



**catch error**
So, on your try and catch section 

      catch (\Magento\Framework\Exception\AlreadyExistsException $e) {
    	$this->messageManager->addError($message);
    }

**For your case you can use below catch handling logic**

    catch (\Magento\Framework\Exception\AlreadyExistsException $e) {
        $message = $this->__('There is already an account with this emails address. If you are sure that it is your email address, <a href="%s">click here</a> to get the password and access your account.', $url);
     $this->_getSession()->addError($message);
    }catch(\Magento\Framework\Exception\LocalizedException $e){
    $message = $e->getMessage();
     $this->_getSession()->addError($message);
    }catch (\Exception $e) {
                $message = $e->getMessage();
     $this->_getSession()->addError($message);
    
    }

  [1]: https://github.com/magento/magento2/tree/2.2-develop/lib/internal/Magento/Framework/Exception