Unexpected "Value Error" error message in build.py

[joey-scanga]

Specs:

OS: Pop!_OS 20.04 LTS x86_64
Host: HP Pavilion Laptop 15-cs3xxx
Kernel: 5.17.5-76051705-generic
Uptime: 1 hour, 37 mins
Packages: 3481 (dpkg), 23 (flatpak), 17 (snap)
Shell: bash 5.0.17
Resolution: 1920x1080
DE: GNOME
WM: Mutter
WM Theme: Pop
Theme: Pop-dark [GTK2/3]
Icons: Pop [GTK2/3]
Terminal: gnome-terminal
CPU: Intel i7-1065G7 (8) @ 3.900GHz
GPU: Intel Iris Plus Graphics G7
GPU: NVIDIA GeForce MX250
Memory: 3582MiB / 15785MiB

After cloning the repository and attempting to run the build.py script in mozilla/, I get this error message:

>>python build.py configure --gcc gcc --gxx g++-4.9 -k 12.10

/usr/lib/python3/dist-packages/requests/__init__.py:89: RequestsDependencyWarning: urllib3 (1.26.9) or chardet (3.0.4) doesn't match a supported version!
  warnings.warn("urllib3 ({}) or chardet ({}) doesn't match a supported "
  File "build.py", line 120
    except ValueError, ex:
                     ^
SyntaxError: invalid syntax