Documented the new error handling functionality from python-http-client

TROUBLESHOOTING.md

@@ -12,6 +12,7 @@ If you can't find a solution below, please open an [issue](https://github.com/se
 * [Using the Package Manager](#package-manager)
 * [Version Convention](#versions)
 * [Viewing the Request Body](#request-body)
+* [Error Handling](#error-handling)
 
 <a name="environment"></a>
 ## Environment Variables and Your SendGrid API Key
@@ -106,3 +107,8 @@ You can do this right before you call `response = sg.client.mail.send.post(reque
 ```python
 print mail.get()
 ```
+
+<a name="error-handling"></a>
+# Error Handling
+
+Please review [our use_cases](https://github.com/sendgrid/sendgrid-python/USE_CASES.md) for examples of error handling.

USE_CASES.md

@@ -7,6 +7,7 @@ This documentation provides examples for specific use cases. Please [open an iss
 * [How to Setup a Domain Whitelabel](#domain_whitelabel)
 * [How to View Email Statistics](#email_stats)
 * [Asynchronous Mail Send](#asynchronous-mail-send)
+* [Error Handling](#error-handling)
 
 <a name="transactional-templates"></a>
 # Transactional Templates
@@ -272,3 +273,30 @@ if __name__ == "__main__":
     loop.run_until_complete(task)
 ```
 
+<a name="error-handling"></a>
+# Error Handling
+[Custom exceptions](https://github.com/sendgrid/python-http-client/blob/master/python_http_client/exceptions.py) for `python_http_client` are now supported, which can be imported by consuming libraries.
+
+Please see [here](https://github.com/sendgrid/python-http-client/blob/master/python_http_client/exceptions.py) for a list of supported exceptions.
+
+```python
+  import sendgrid
+  import os
+  from sendgrid.helpers.mail import *
+  from python_http_client import exceptions
+
+  sg = sendgrid.SendGridAPIClient(apikey=os.environ.get('SENDGRID_API_KEY'))
+  from_email = Email("dx@sendgrid.com")
+  to_email = Email("elmer.thomas@sendgrid.com")
+  subject = "Sending with SendGrid is Fun"
+  content = Content("text/plain", "and easy to do anywhere, even with Python")
+  mail = Mail(from_email, subject, to_email, content)
+  try:
+      response = sg.client.mail.send.post(request_body=mail.get())
+  except exceptions.BadRequestsError as e:
+      print(e.body)
+      exit()
+  print(response.status_code)
+  print(response.body)
+  print(response.headers)
+```