Update TROUBLESHOOTING.md

Author: thinkingserious

TROUBLESHOOTING.md

@@ -45,6 +45,8 @@ Click the "Clone or download" green button in [GitHub](https://github.com/sendgr
 To read the error message returned by SendGrid's API:
 
 ```python
+import urllib2
+
 try:
   response = sg.client.mail.send.post(request_body=mail.get())
 except urllib2.HTTPError as e:
@@ -82,4 +84,4 @@ In most cases we recommend you download the latest version of the library, but i
 
 If you are usring a [requirements file](https://pip.readthedocs.io/en/1.1/requirements.html), please use:
 
-`sendgrid==X.X.X`
+`sendgrid==X.X.X`