Exception classes redesign

Replacing 1 exception class with 3 more specific classes: 
HTTP Exception (server returned http code != 200), 
Invalid JSON Exception (server returned invalid json),
Telegram Expection (telegram returned ok != true)

All 3 classes extend BaseApiException so we can handle all API exceptions at the same time

telebot/apihelper.py

@@ -116,27 +116,22 @@ def _check_result(method_name, result):
         - The content of the result is invalid JSON.
         - The method call was unsuccessful (The JSON 'ok' field equals False)
 
-    :raises ApiException: if one of the above listed cases is applicable
+    :raises BaseApiException: if one of the above listed cases is applicable
     :param method_name: The name of the method called
     :param result: The returned result of the method request
     :return: The result parsed to a JSON dictionary.
     """
     if result.status_code != 200:
-        msg = 'The server returned HTTP {0} {1}. Response body:\n[{2}]' \
-            .format(result.status_code, result.reason, result.text.encode('utf8'))
-        raise ApiException(msg, method_name, result)
+        raise ApiHTTPException(method_name, result)
 
     try:
         result_json = result.json()
     except:
-        msg = 'The server returned an invalid JSON response. Response body:\n[{0}]' \
-            .format(result.text.encode('utf8'))
-        raise ApiException(msg, method_name, result)
+        raise ApiInvalidJSONException(method_name, result)
 
     if not result_json['ok']:
-        msg = 'Error code: {0} Description: {1}' \
-            .format(result_json['error_code'], result_json['description'])
-        raise ApiException(msg, method_name, result)
+        raise ApiTelegramException(msg, method_name, result, result_json)
+        
     return result_json
 
 
@@ -165,9 +160,8 @@ def download_file(token, file_path):
         
     result = _get_req_session().get(url, proxies=proxy)
     if result.status_code != 200:
-        msg = 'The server returned HTTP {0} {1}. Response body:\n[{2}]' \
-            .format(result.status_code, result.reason, result.text)
-        raise ApiException(msg, 'Download file', result)
+        raise ApiHTTPException('Download file', result)
+        
     return result.content
 
 
@@ -1245,15 +1239,52 @@ def _no_encode(func):
     return wrapper
 
 
-class ApiException(Exception):
+class BaseApiException(Exception):
     """
-    This class represents an Exception thrown when a call to the Telegram API fails.
+    This class represents a base Exception thrown when a call to the Telegram API fails.
     In addition to an informative message, it has a `function_name` and a `result` attribute, which respectively
     contain the name of the failed function and the returned result that made the function to be considered  as
     failed.
     """
 
     def __init__(self, msg, function_name, result):
-        super(ApiException, self).__init__("A request to the Telegram API was unsuccessful. {0}".format(msg))
+        super(BaseApiException, self).__init__("A request to the Telegram API was unsuccessful. {0}".format(msg))
         self.function_name = function_name
         self.result = result
+    
+class ApiHTTPException(BaseApiException):
+    """
+    This class represents an Exception thrown when a call to the 
+    Telegram API server returns HTTP code that is not 200.
+    """
+    def __init__(self, function_name, result):
+        super(ApiHTTPException, self).__init__(
+            "The server returned HTTP {0} {1}. Response body:\n[{2}]" \
+            .format(result.status_code, result.reason, result.text.encode('utf8')),
+            function_name,
+            result)
+    
+class ApiInvalidJSONException(BaseApiException):
+    """
+    This class represents an Exception thrown when a call to the 
+    Telegram API server returns invalid json.
+    """
+    def __init__(self, function_name, result):
+        super(ApiInvalidJSONException, self).__init__(
+            "The server returned an invalid JSON response. Response body:\n[{0}]" \
+            .format(result.text.encode('utf8')),
+            function_name,
+            result)
+    
+class ApiTelegramException(BaseApiException):
+    """
+    This class represents an Exception thrown when a Telegram API returns error code.
+    """
+    def __init__(self, function_name, result, result_json):
+        super(ApiTelegramException, self).__init__(
+            "Error code: {0} Description: {1}" \
+            .format(result_json['error_code'], result_json['description']),
+            function_name,
+            result)
+        self.result_json = result_json
+