[Discuss-gnuradio] Error in Python file generated by GnuRadio Companion

Hello,

I have created My QPSK Demodulator following tutorial 4:
https://gnuradio.org/redmine/projects/gnuradio/wiki/Guided_Tutorial_GNU_Radio_in_C++

My source files (C++, XML) look exactly like those in the repository and
the build and installation produced the same output as shown in the
tutorial.

I have created a .gnuradio/config.conf file in my home directory so that
I could add the XML installation file to GRC search path:

[grc]
local_blocks_path=/usr/local/share/gnuradio/grc/blocks

My QPSK Demodulator appears correctly in GRC and I could connect the
block in the attached GRC application (source and screenshot attached).

However, when I click on the "Generate the flow graph" button, the
Python file generated has the following lines:

self.tutorial_my_qpsk_demod_cb_0 = -------->
cannot find 'Gray_code': tutorial.my_qpsk_demod_cb($Gray_code)
<--------

And if I execute the graph, the following error happens, unsurprisingly:

Executing: "/home/dpi/projects/seethroughwalls/CHa/mpsk_stage6.py"

File "/home/dpi/projects/seethroughwalls/CHa/mpsk_stage6.py", line 197
self.tutorial_my_qpsk_demod_cb_0 = -------->
^
SyntaxError: invalid syntax

My configuration:

Ubuntu 14.04
GNU Radio Companion 3.7.2.1
GNU Radio 3.7.2.1

All installed via Ubuntu packages.

I am sure this is a simple thing, but unfortunately my investigations so
far have been unsuccessful. Any help would be appreciated.

Best regards,
Damien