Help to upgrade to 21.5 please

[Mick Sulley]

Running Linux Mint 20.1

I have Eric 20.10 installed and working and I am trying to move to 21.5 
and I am stuck.  I am sure it is my lack of understanding rather than 
anything wrong with the software, but I would appreciate some help.

Following the instructions on 
https://eric-ide.python-projects.org/eric-download.html

Downloaded and extracted the package - this is what I see then

mick at Mint20Desk:~/.eric6-21/eric6-21.5$ sudo python3 install.py
Checking dependencies
Python Version: 3.8.5
Found PyQt5
Found pyuic5
Optional 'PyQtWebEngine' could not be detected.
Optional 'PyQtChart' could not be detected.
Sorry, please install QScintilla2 and
its PyQt5 wrapper.
Error: QScintilla could not be installed.

How do I install QScintilla2 and its PyQt5 wrapper?  Looking in Synaptic 
pyqt5 and pyqt5.qsci-dev are installed

Thanks

Mick