Avoid closing files multiple times in getInterpreter(#17665)

Co-authored-by: autofix-ci[bot] <114827586+autofix-ci[bot]@users.noreply.github.com>
Co-authored-by: fisker Cheung <lionkay@gmail.com>

changelog_unreleased/misc/17665.md

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+#### Avoid closing files multiple times (#17665 by @43081j)
+
+When reading a file to infer the interpreter from a shebang, we use the
+`n-readlines` library to read the first line in order to get the shebang.
+
+This library closes files when it reaches EOF, and we later try close the same
+files again. We now close files only if `n-readlines` did not already close
+them.