Fix CVE-2018-1000802:

https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2018-1000802

Taken from upstream commit (sans NEWS):
https://github.com/python/cpython/commit/d8b103b8b3ef9644805341216963a64098642435

diff --git a/Lib/shutil.py b/Lib/shutil.py
index 3462f7c5e9..0ab1a06f52 100644
--- a/Lib/shutil.py
+++ b/Lib/shutil.py
@@ -413,17 +413,21 @@ def _make_tarball(base_name, base_dir, compress="gzip", verbose=0, dry_run=0,
 
     return archive_name
 
-def _call_external_zip(base_dir, zip_filename, verbose=False, dry_run=False):
+def _call_external_zip(base_dir, zip_filename, verbose, dry_run, logger):
     # XXX see if we want to keep an external call here
     if verbose:
         zipoptions = "-r"
     else:
         zipoptions = "-rq"
-    from distutils.errors import DistutilsExecError
-    from distutils.spawn import spawn
+    cmd = ["zip", zipoptions, zip_filename, base_dir]
+    if logger is not None:
+        logger.info(' '.join(cmd))
+    if dry_run:
+        return
+    import subprocess
     try:
-        spawn(["zip", zipoptions, zip_filename, base_dir], dry_run=dry_run)
-    except DistutilsExecError:
+        subprocess.check_call(cmd)
+    except subprocess.CalledProcessError:
         # XXX really should distinguish between "couldn't find
         # external 'zip' command" and "zip failed".
         raise ExecError, \
@@ -458,7 +462,7 @@ def _make_zipfile(base_name, base_dir, verbose=0, dry_run=0, logger=None):
         zipfile = None
 
     if zipfile is None:
-        _call_external_zip(base_dir, zip_filename, verbose, dry_run)
+        _call_external_zip(base_dir, zip_filename, verbose, dry_run, logger)
     else:
         if logger is not None:
             logger.info("creating '%s' and adding '%s' to it",
539f3ad1d30967950f9bf3a1b7ad271ba3360'/><select name='qt'>
<option value='grep'>log msg</option>
<option value='author'>author</option>
<option value='committer'>committer</option>
<option value='range'>range</option>
</select>
<input class='txt' type='search' size='10' name='q' value=''/>
<input type='submit' value='search'/>
</form>
</td></tr></table>
<div class='path'>path: <a href='/guix/log/?id=871539f3ad1d30967950f9bf3a1b7ad271ba3360'>root</a>/<a href='/guix/log/build-aux?id=871539f3ad1d30967950f9bf3a1b7ad271ba3360'>build-aux</a>/<a href='/guix/log/build-aux/cuirass?id=871539f3ad1d30967950f9bf3a1b7ad271ba3360'>cuirass</a>/<a href='/guix/log/build-aux/cuirass/hydra-to-cuirass.scm?id=871539f3ad1d30967950f9bf3a1b7ad271ba3360'>hydra-to-cuirass.scm</a></div><div class='content'><table class='list nowrap'><tr class='nohover'><th class='left'>Age</th><th class='left'>Commit message (<a href='/guix/log/build-aux/cuirass/hydra-to-cuirass.scm?id=871539f3ad1d30967950f9bf3a1b7ad271ba3360&amp;showmsg=1'>Expand</a>)</th><th class='left'>Author</th></tr>
<tr><td><span title='2018-04-08 17:48:33 +0200'>2018-04-08</span></td><td><a href='/guix/commit/build-aux/cuirass/hydra-to-cuirass.scm?id=a1ec7540be9b30593f5e83e36a0e83b1bcf337f1'>cuirass: Factorize hydra-to-cuirass CI job translation.</a><span class='msg-avail'>...<span class='msg-tooltip'>* build-aux/cuirass/gnu-system.scm: Move code to...
* build-aux/cuirass/hydra-to-cuirass.scm: ... here, and include it.
* Makefile.am (EXTRA_DIST): Add 'build-aux/cuirass/hydra-to-cuirass.scm'
and 'build-aux/cuirass/gnu-system.scm'.
</span></span></td><td>Ludovic Courtès</td></tr>