Async def invalid syntax

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I installed now python3.7, but I am now getting this error:

Could not find platform independent libraries <prefix>
Could not find platform dependent libraries <exec_prefix>
Consider setting $PYTHONHOME to <prefix>[:<exec_prefix>]
Fatal Python error: initfsencoding: Unable to get the locale encoding
ModuleNotFoundError: No module named 'encodings'

Current thread 0x00007f43c577b740 (most recent call first):
Aborted