py/mpz: Use assert to verify mpz does not have a fixed digit buffer.
py/mpz: Use assert to verify mpz does not have a fixed digit buffer.

dxxb/micropython,dmazzella/micropython,SHA2017-badge/micropython-esp32,alex-robbins/micropython,Peetz0r/micropython-esp32,cwyark/micropython,jmarcelino/pycom-micropython,tobbad/micropython,Peetz0r/micropython-esp32,dxxb/micropython,swegener/micropython,blazewicz/micropython,SHA2017-badge/micropython-esp32,swegener/micropython,Timmenem/micropython,MrSurly/micropython-esp32,MrSurly/micropython,adafruit/circuitpython,deshipu/micropython,pozetroninc/micropython,MrSurly/micropython-esp32,MrSurly/micropython-esp32,selste/micropython,micropython/micropython-esp32,lowRISC/micropython,adafruit/circuitpython,trezor/micropython,cwyark/micropython,SHA2017-badge/micropython-esp32,matthewelse/micropython,selste/micropython,dxxb/micropython,puuu/micropython,ryannathans/micropython,dmazzella/micropython,chrisdearman/micropython,henriknelson/micropython,AriZuu/micropython,pfalcon/micropython,selste/micropython,MrSurly/micropython-esp32,toolmacher/micropython,toolmacher/micropython,mhoffma/micropython,deshipu/micropython,torwag/micropython,HenrikSolver/micropython,alex-march/micropython,HenrikSolver/micropython,selste/micropython,bvernoux/micropython,cwyark/micropython,mhoffma/micropython,bvernoux/micropython,alex-march/micropython,SHA2017-badge/micropython-esp32,HenrikSolver/micropython,micropython/micropython-esp32,dxxb/micropython,hosaka/micropython,hiway/micropython,tobbad/micropython,HenrikSolver/micropython,dxxb/micropython,puuu/micropython,infinnovation/micropython,dmazzella/micropython,adafruit/micropython,oopy/micropython,pramasoul/micropython,matthewelse/micropython,tobbad/micropython,adafruit/micropython,blazewicz/micropython,puuu/micropython,deshipu/micropython,blazewicz/micropython,bvernoux/micropython,PappaPeppar/micropython,cwyark/micropython,SHA2017-badge/micropython-esp32,TDAbboud/micropython,tuc-osg/micropython,PappaPeppar/micropython,swegener/micropython,oopy/micropython,MrSurly/micropython-esp32,mhoffma/micropython,AriZuu/micropython,pfalcon/micropython,tralamazza/micropython,alex-march/micropython,toolmacher/micropython,hosaka/micropython,kerneltask/micropython,torwag/micropython,hosaka/micropython,lowRISC/micropython,chrisdearman/micropython,adafruit/circuitpython,ryannathans/micropython,adafruit/circuitpython,pfalcon/micropython,ryannathans/micropython,trezor/micropython,pozetroninc/micropython,matthewelse/micropython,hiway/micropython,blazewicz/micropython,pozetroninc/micropython,adafruit/micropython,kerneltask/micropython,AriZuu/micropython,TDAbboud/micropython,TDAbboud/micropython,Timmenem/micropython,tralamazza/micropython,deshipu/micropython,TDAbboud/micropython,puuu/micropython,pfalcon/micropython,chrisdearman/micropython,MrSurly/micropython,trezor/micropython,Peetz0r/micropython-esp32,PappaPeppar/micropython,pramasoul/micropython,ryannathans/micropython,lowRISC/micropython,henriknelson/micropython,tralamazza/micropython,MrSurly/micropython,ryannathans/micropython,pfalcon/micropython,puuu/micropython,tuc-osg/micropython,micropython/micropython-esp32,micropython/micropython-esp32,hiway/micropython,tuc-osg/micropython,kerneltask/micropython,tobbad/micropython,jmarcelino/pycom-micropython,adafruit/circuitpython,alex-robbins/micropython,AriZuu/micropython,matthewelse/micropython,deshipu/micropython,mhoffma/micropython,oopy/micropython,alex-robbins/micropython,toolmacher/micropython,tobbad/micropython,pramasoul/micropython,adafruit/circuitpython,kerneltask/micropython,infinnovation/micropython,hosaka/micropython,lowRISC/micropython,adafruit/micropython,torwag/micropython,blazewicz/micropython,Timmenem/micropython,alex-robbins/micropython,henriknelson/micropython,PappaPeppar/micropython,TDAbboud/micropython,pozetroninc/micropython,tralamazza/micropython,chrisdearman/micropython,Peetz0r/micropython-esp32,matthewelse/micropython,bvernoux/micropython,Timmenem/micropython,lowRISC/micropython,oopy/micropython,cwyark/micropython,Timmenem/micropython,micropython/micropython-esp32,trezor/micropython,alex-robbins/micropython,henriknelson/micropython,infinnovation/micropython,pramasoul/micropython,torwag/micropython,oopy/micropython,infinnovation/micropython,torwag/micropython,AriZuu/micropython,tuc-osg/micropython,matthewelse/micropython,bvernoux/micropython,henriknelson/micropython,tuc-osg/micropython,Peetz0r/micropython-esp32,mhoffma/micropython,hosaka/micropython,chrisdearman/micropython,jmarcelino/pycom-micropython,jmarcelino/pycom-micropython,infinnovation/micropython,alex-march/micropython,HenrikSolver/micropython,swegener/micropython,dmazzella/micropython,kerneltask/micropython,swegener/micropython,adafruit/micropython,selste/micropython,alex-march/micropython,jmarcelino/pycom-micropython,hiway/micropython,MrSurly/micropython,PappaPeppar/micropython,pozetroninc/micropython,trezor/micropython,hiway/micropython,MrSurly/micropython,toolmacher/micropython,pramasoul/micropython