Fix packet output in Python 3

[argilo]

On Python 3, RFlisten fails to print received packets:

TypeError                                 Traceback (most recent call last)
~/git/rfcat/rflib/__init__.py in <module>
      6 d.setMdmSyncWord(0x02dd4)
      7 d.makePktVLEN()
----> 8 d.RFlisten()

~/git/rfcat/rflib/chipcon_nic.py in RFlisten(self)
   1211             try:
   1212                 y, t = self.RFrecv()
-> 1213                 print("(%5.3f) Received:  %s  | %s" % (t, hexlify(y), makeFriendlyAscii(y)))
   1214 
   1215             except ChipconUsbTimeoutException:

~/git/rfcat/rflib/chipcon_nic.py in makeFriendlyAscii(instring)
     44         out.append( instring[ start: ] )
     45 
---> 46     return b''.join(out)
     47 
     48 

TypeError: sequence item 1: expected a bytes-like object, str found

I rewrote and simplified makeFriendlyAscii to correct this problem. It also now returns a string instead of bytes, to avoid being printed as b'.......).\."u..'. I also added .decode() after each call to hexlify to avoid the hex being printed as b'010c0101019f8d29f55cef22750791'.

After these changes, packets are printed the same in Python 2 and Python 3.

[atlas0fd00m]

thanks @argilo , i'm tempted to accept this just for the white-space cleanup. :)

i like the simplication, and i'm really happy to get strings instead of bytes. however, it creates a new string for every character, which is very costly for Python (or at least it was in Python2). could you take another go at it using lists and one string creation at the end?

in the interim, i just committed and pushed a new bit of code to solve this makeFriendlyAscii() bug. please test and see if it's broken.

[argilo]

i'm tempted to accept this just for the white-space cleanup.

The whitespace cleanup is in a separate commit, so you could still cherry-pick that.

[argilo]

@atlas0fd00m Your change does fix the crash; the only problem that remains is that the bytes are printed in their repr() form:

(1601174272.130) Received:  b'010a010101b8143d7533b98626db8f'  | b'.......=u3..&..'
(1601174284.359) Received:  b'010c0101019f8d29f55cef22750791'  | b'.......).\\."u..'
(1601174291.225) Received:  b'010d010101e9395df5c4cb7a32219f'  | b'......9]...z2!.'

[argilo]

I'll close off this pull request for now, since the problems it was meant to solve are mostly gone now.

[atlas0fd00m]

@argilo thank you for your submission. we can make the output a string if that makes sense. i'm still getting my sea-legs with strings and bytes with py3. what do you think?