python@3.8: use f-string in sitecustomize.py

Formula/python@3.8.rb

@@ -355,9 +355,10 @@ class PythonAT38 < Formula
           # because the PYTHONPATH is evaluated after the sitecustomize.py. Many modules (e.g. PyQt4) are
           # built only for a specific version of Python and will fail with cryptic error messages.
           # In the end this means: Don't set the PYTHONPATH permanently if you use different Python versions.
-          exit('Your PYTHONPATH points to a site-packages dir for Python 3.x but you are running Python ' +
-               str(sys.version_info[0]) + '.x!\\n     PYTHONPATH is currently: "' + str(os.environ['PYTHONPATH']) + '"\\n' +
-               '     You should `unset PYTHONPATH` to fix this.')
+          exit(f'Your PYTHONPATH points to a site-packages dir for Python 3.x '
+               f'but you are running Python {sys.version_info[0]}.x!\\n'
+               f'     PYTHONPATH is currently: "{os.environ["PYTHONPATH"]}"\\n'
+               f'     You should `unset PYTHONPATH` to fix this.')
       # Only do this for a brewed python:
       if os.path.realpath(sys.executable).startswith('#{rack}'):
           # Shuffle /Library site-packages to the end of sys.path
@@ -369,7 +370,7 @@ class PythonAT38 < Formula
           # the Cellar site-packages is a symlink to the HOMEBREW_PREFIX
           # site_packages; prefer the shorter paths
           long_prefix = re.compile(r'#{rack}/[0-9._abrc]+/Frameworks/Python.framework/Versions/#{version.major_minor}/lib/python#{version.major_minor}/site-packages')
-          sys.path = [long_prefix.sub('#{HOMEBREW_PREFIX/"lib/python#{version.major_minor}/site-packages"}', p) for p in sys.path]
+          sys.path = [long_prefix.sub('#{site_packages}', p) for p in sys.path]
           # Set the sys.executable to use the opt_prefix. Only do this if PYTHONEXECUTABLE is not
           # explicitly set and we are not in a virtualenv:
           if 'PYTHONEXECUTABLE' not in os.environ and sys.prefix == sys.base_prefix: