Installation on Python 3.6 throws an error while compiling

[4027/6612] Generating subprojects/FFmpeg/avutil-def with a custom command (wrapped by meson to capture output)
FAILED: subprojects/FFmpeg/avutil.def 
/usr/local/bin/meson --internal exe --capture subprojects/FFmpeg/avutil.def -- /usr/bin/python3 /src/gstreamer/subprojects/FFmpeg/compat/windows/makedef.py --nm /usr/bin/nm --prefix '' /src/gstreamer/builddir/subprojects/FFmpeg/libavutil/libavutil.ver /src/gstreamer/builddir/subprojects/FFmpeg/libavutil-static.a
--- stderr ---
Traceback (most recent call last):
  File "/src/gstreamer/subprojects/FFmpeg/compat/windows/makedef.py", line 74, in <module>
    '-g', libname], capture_output=True, text=True, check=True)
  File "/usr/lib/python3.6/subprocess.py", line 423, in run
    with Popen(*popenargs, **kwargs) as process:
TypeError: __init__() got an unexpected keyword argument 'capture_output'

[4028/6612] Compiling C object subprojects/FFmpeg/test_avutil_color_utils.p/libavutil_tests_color_utils.c.o
[4029/6612] Linking target subprojects/FFmpeg/test_avutil_cpu
ninja: build stopped: subcommand failed.

On Ubuntu 18.04 with the default Python 3.6 version. Build fails on 1.20.3 and 1.20.4. capture_output is only on Python 3.7+, more compatible way is to use stdout=subprocess.PIPE, stderr=subprocess.PIPE on subprocess.run.