Fixup realpath polyfill (#3123)
Fixup realpath polyfill (#3123)

Added in #3103, but https://github.com/neuropoly/spinalcordtoolbox/runs/1601504567?check_suite_focus=true#step:4:1407 shows it failing with

>   File "<string>", line 1
>    import sys, path; for f in sys.argv[1:]: print(os.path.realpath(f))
>                        ^
> SyntaxError: invalid syntax

I guess I didn't actually test this.
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