bpo-32713: Fix tarfile.itn for large/negative float values. (GH-5434)

(cherry picked from commit 72d9b2be36f091793ae7ffc5ad751f040c6e6ad3)

Co-authored-by: Joffrey F <f.joffrey@gmail.com>
diff --git a/Lib/tarfile.py b/Lib/tarfile.py
index a24ee42..85119a4 100755
--- a/Lib/tarfile.py
+++ b/Lib/tarfile.py
@@ -200,8 +200,9 @@
     # base-256 representation. This allows values up to (256**(digits-1))-1.
     # A 0o200 byte indicates a positive number, a 0o377 byte a negative
     # number.
+    n = int(n)
     if 0 <= n < 8 ** (digits - 1):
-        s = bytes("%0*o" % (digits - 1, int(n)), "ascii") + NUL
+        s = bytes("%0*o" % (digits - 1, n), "ascii") + NUL
     elif format == GNU_FORMAT and -256 ** (digits - 1) <= n < 256 ** (digits - 1):
         if n >= 0:
             s = bytearray([0o200])