Added custom errors, fixes to code generator

The code generator now handles okay the flags using True type
Also, double checking for the flag is now avoided in cases where the
flag was a Vector type

errors.py

@@ -0,0 +1,82 @@
+class InvalidParameterError(Exception):
+    """Occurs when an invalid parameter is given, for example,
+    when either A or B are required but none is given"""
+
+
+class TypeNotFoundError(Exception):
+    """Occurs when a type is not found, for example,
+    when trying to read a TLObject with an invalid constructor code"""
+    def __init__(self, invalid_constructor_id):
+        super().__init__(self, 'Could not find a matching Constructor ID for the TLObject '
+                               'that was supposed to be read with ID {}. Most likely, a TLObject '
+                               'was trying to be read when it should not be read.'
+                               .format(hex(invalid_constructor_id)))
+
+        self.invalid_constructor_id = invalid_constructor_id
+
+
+class InvalidDCError(Exception):
+    def __init__(self, new_dc):
+        super().__init__(self,  'Your phone number is registered to #{} DC. '
+                                'This should have been handled automatically; '
+                                'if it has not, please restart the app.')
+
+        self.new_dc = new_dc
+
+
+class InvalidChecksumError(Exception):
+    def __init__(self, checksum, valid_checksum):
+        super().__init__(self,  'Invalid checksum ({} when {} was expected). This packet should be skipped.'
+                                .format(checksum, valid_checksum))
+
+        self.checksum = checksum
+        self.valid_checksum = valid_checksum
+
+
+class RPCError(Exception):
+    def __init__(self, message):
+        super().__init__(self, message)
+        self.message = message
+
+
+class BadMessageError(Exception):
+    """Occurs when handling a bad_message_notification"""
+    ErrorMessages = {
+        16: 'msg_id too low (most likely, client time is wrong it would be worthwhile to '
+            'synchronize it using msg_id notifications and re-send the original message '
+            'with the “correct” msg_id or wrap it in a container with a new msg_id if the '
+            'original message had waited too long on the client to be transmitted).',
+
+        17: 'msg_id too high (similar to the previous case, the client time has to be '
+            'synchronized, and the message re-sent with the correct msg_id).',
+
+        18: 'Incorrect two lower order msg_id bits (the server expects client message msg_id '
+            'to be divisible by 4).',
+
+        19: 'Container msg_id is the same as msg_id of a previously received message '
+            '(this must never happen).',
+
+        20: 'Message too old, and it cannot be verified whether the server has received a '
+            'message with this msg_id or not.',
+
+        32: 'msg_seqno too low (the server has already received a message with a lower '
+            'msg_id but with either a higher or an equal and odd seqno).',
+
+        33: 'msg_seqno too high (similarly, there is a message with a higher msg_id but with '
+            'either a lower or an equal and odd seqno).',
+
+        34: 'An even msg_seqno expected (irrelevant message), but odd received.',
+
+        35: 'Odd msg_seqno expected (relevant message), but even received.',
+
+        48: 'Incorrect server salt (in this case, the bad_server_salt response is received with '
+            'the correct salt, and the message is to be re-sent with it).',
+
+        64: 'Invalid container.'
+    }
+
+    def __init__(self, code):
+        super().__init__(self, BadMessageError
+                         .ErrorMessages.get(code,'Unknown error code (this should not happen): {}.'.format(code)))
+
+        self.code = code