Fix 'sed: RE error: illegal byte sequence'

[tuzi3040]

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• My PR addresses the following pyenv issue (if any)
  • `pyenv help realpath.dylib' results in "sed: RE error: illegal byte sequence" #1454

Description

• Here are some details about my PR
  Fix 'sed: RE error: illegal byte sequence'
  by unsetting LC_ALL and passing LC_CTYPE=C to sed.

Tests

• My PR adds the following unit tests (if any)