TypeError: can only concatenate str (not "bytes") to str

edit

Hello.

I am trying to use the canusb package on ROS Noetic (installed on Raspberry PI OS x64) but the problem is this package is written on python2 but Noetic uses python3 so there are some incompatibilities.

When I am trying to run the package the following error appears:

Traceback (most recent call last):
  File "/home/pi/catkin_ws/src/canusb/script/canusb.py", line 191, in <module>
    can.init()
  File "/home/pi/catkin_ws/src/canusb/script/canusb.py", line 57, in init
    line = self.readline()
  File "/home/pi/catkin_ws/src/canusb/script/canusb.py", line 51, in readline
    ret += c
TypeError: can only concatenate str (not "bytes") to str

The code lines on the package are:

def readline(self):
            """
            Overrides io.RawIOBase.readline which cannot handle with '\r' delimiters
            """
            ret = ''
            while True:
                c = self.read(1)
                if c == '':
                    return ret
                elif c == '\r':
                    if ret == 'z' or ret == 'Z':
                        self.status = 0
                    return ret + c
                elif c == chr(7):
                    self.status = -1
                    return c
                else:
                    ret += c

What can I change to fix the problem up?

Thnaks in advance.

Best regards. Alessandro

EDIT

Appear the following errors:[ERROR][]: Disable timestamp: Failed! and [ERROR][]: Disable baudrate: Failed!. I post the links of the original and the modified code below.

Original

Modified

I hope with this anyone can help me. Best regards.