If we continue supporting 3.4 then we're stuck with current versions of packages. Most importantly, we will miss the security fixes in the latest versions of the packages.
I suggest, pgAdmin should drop support for 3.4 and support only python 3.5 and above.
End of life dates for Python versions, so eventually Python 3.5 also reached EOL
Python 3.4: reached End Of Life
Python 3.5: security fixes only, no bug fixes will be provided; End Of Life: 2020-09-13
Python 3.6: security fixes only, no bug fixes will be provided; End Of Life: 2021-12-23
Python 3.7: security fixes AND bug fixes will be provided; End Of Life: 2023-06-27
Python 3.8: security fixes AND bug fixes will be provided; End Of Life: 2024-10