Fix decoding of v5 messages with overall property length > 127 bytes.

Closes #541. Thanks to ochabloz.

Author: ralight

ChangeLog.txt

@@ -1,3 +1,6 @@
+- Fix incoming MQTT v5 messages with overall property length > 127 bytes being
+incorrectly decoded. Closes #541.
+
 v1.5.1 - 2020x-09-22
 ===================
 

src/paho/mqtt/properties.py

@@ -391,10 +391,10 @@ def unpack(self, buffer):
         buffer = buffer[VBIlen:]  # strip the bytes used by the VBI
         propslenleft = propslen
         while propslenleft > 0:  # properties length is 0 if there are none
-            identifier, VBIlen = VariableByteIntegers.decode(
+            identifier, VBIlen2 = VariableByteIntegers.decode(
                 buffer)  # property identifier
-            buffer = buffer[VBIlen:]  # strip the bytes used by the VBI
-            propslenleft -= VBIlen
+            buffer = buffer[VBIlen2:]  # strip the bytes used by the VBI
+            propslenleft -= VBIlen2
             attr_type = self.properties[identifier][0]
             value, valuelen = self.readProperty(
                 buffer, attr_type, propslenleft)