How to fix gstreamer1 build error?

Hi All,

I'm using branch openwrt-19.07 and trying to build gstreamer1.
Build error like

Traceback (most recent call last):
  File "/home/builder/workdir/s5lwrt/staging_dir/hostpkg/lib/meson/meson.py", line 26, in <module>
    from mesonbuild import mesonmain
  File "/home/builder/workdir/s5lwrt/staging_dir/hostpkg/lib/meson/mesonbuild/mesonmain.py", line 23, in <module>
    from . import mesonlib
  File "/home/builder/workdir/s5lwrt/staging_dir/hostpkg/lib/meson/mesonbuild/mesonlib.py", line 67
    def git(cmd: T.List[str], workingdir: str, **kwargs: T.Any) -> subprocess.CompletedProcess:
               ^
SyntaxError: invalid syntax
Makefile:238: recipe for target '/home/builder/workdir/s5lwrt/build_dir/target-aarch64-linux-gnu_glibc/gstreamer-1.17.1/.configured_a17fb5ef857664f03cd0ce37cc5ea591' failed

How to fix it? Please help. Thanks.

Switch ubuntu version to 18.04. Anything looks good.