Firmware Transfer bug in Python

Hi Mikko,

I was unsuccessfully trying to use Python for the meter's firmware upgrade. After analysing the source code of the GXDLMSImageTransfer.py class, and compare with C# and C++ library I see that there are some descripencies in the method imageBlockTransfer()

[SNIP]
def imageBlockTransfer(self, client, imageBlockValue, imageBlockCount):
cnt = len(imageBlockValue)
if (cnt % self.imageBlockSize) != 0:
cnt += 1
[SNIP]
pos = 0
while pos != cnt:
<Processing...>
pos += 1
[SNIP]

The problem that cnt is set to the size of the image and we are traversing byte by byte instead of the block.

It is nessesary to chenge the first few lines in the method to:

[SNIP]
cnt = int(len(imageBlockValue)/self.imageBlockSize);
if len(imageBlockValue) % self.imageBlockSize != 0:
cnt +=1;
[SNIP]

After that modification, which is in line with C# version, everything started to work as expected.

I hope that this change will be added into the next release.

Kind regards,
Ilya