gem5 scons build fails with "TypeError: argument should be integer or bytes-like object, not 'str'" - scons

Question

I am trying to install gem5 on a fresh installation of Ubuntu 20.04 and using commit 9fc9c67b4242c03f165951775be5cd0812f2a705. I have used
http://learning.gem5.org/book/part1/building.html
and
https://www.gem5.org/documentation/general_docs/building
as my guide. As near as I can tell, I have installed all the required dependencies using (some dependencies are repeated in these two lines)
sudo apt install build-essential git m4 scons zlib1g zlib1g-dev libprotobuf-dev protobuf-compiler libprotoc-dev libgoogle-perftools-dev python-dev python
sudo apt install build-essential git m4 scons zlib1g zlib1g-dev \
libprotobuf-dev protobuf-compiler libprotoc-dev libgoogle-perftools-dev \
python-dev python libboost-all-dev
Then, when I try to build gem5 using
git clone https://gem5.googlesource.com/public/gem5
cd gem5
scons build/X86/gem5.opt -j8
I get the following output after executing the 'scons' line:
scons: Reading SConscript files ...
Warning: Failed to find git repo directory: a bytes-like object is required, not 'str'
TypeError: argument should be integer or bytes-like object, not 'str':
File "/home/john/gem5/SConstruct", line 355:
main['GCC'] = CXX_version and CXX_version.find('g++') >= 0
I am not sure how to fix this error or even why this error is occurring; I don't even really know what this error is saying. Any help would be appreciated.

Answer 1

Yes. That's the result of running a build system implemented in scons expecting only python2.
If you're stuck here's what you can do to be able to compile until the gem project pushes their Python 3 + SCons changes.
sudo apt-get install virtualenv
# create a virtualenv which uses python 2.7
virtualenv -p python2.7 venv27
# activate the virtualenv
. venv27/bin/activate
# Install SCons in the python 2.7 virtualenv
pip install scons
# This will now use the scons installed in a python 2.7 virtualenv.
scons build/X86/gem5.opt -j8
This worked for me on an Ubuntu 20.04 system.