docs: improve quickstart POST and status handling examples

docs/user/quickstart.rst

@@ -271,9 +271,12 @@ use the same key::
       },
       ...
     }
-    >>> r1.text == r2.text
+    >>> r1.json()['form'] == r2.json()['form']
     True
 
+The complete response text may differ between requests (for example, due to
+headers added by ``httpbin``), but the form payload is equivalent.
+
 There are times that you may want to send data that is not form-encoded. If
 you pass in a ``string`` instead of a ``dict``, that data will be posted directly.
 
@@ -399,6 +402,20 @@ But, since our ``status_code`` for ``r`` was ``200``, when we call
     >>> r.raise_for_status()
     None
 
+For complete status/error handling in one example::
+
+    >>> import requests
+    >>> from requests.exceptions import HTTPError
+    >>> try:
+    ...     response = requests.get('https://api.github.com')
+    ...     response.raise_for_status()
+    ... except HTTPError as http_err:
+    ...     print(f'HTTP error occurred: {http_err}')
+    ... except Exception as err:
+    ...     print(f'Other error occurred: {err}')
+    ... else:
+    ...     print('Success!')
+
 All is well.