Close #12114: fix a potential deadlock in packaging.util._find_exe_version()

Avoid also zombi processes: Popen.communicate() calls its wait() method.

Lib/packaging/tests/test_util.py

@@ -74,6 +74,9 @@ class FakePopen:
             self.stdout = StringIO(exes[self.cmd])
             self.stderr = StringIO()
 
+    def communicate(self, input=None, timeout=None):
+        return self.stdout.read(), self.stderr.read()
+
 
 class UtilTestCase(support.EnvironRestorer,
                    support.TempdirManager,

Lib/packaging/util.py

@@ -464,7 +464,7 @@ def _find_exe_version(cmd, pattern=_RE_VERSION):
         return None
     pipe = Popen(cmd, shell=True, stdout=PIPE, stderr=PIPE)
     try:
-        stdout, stderr = pipe.stdout.read(), pipe.stderr.read()
+        stdout, stderr = pipe.communicate()
     finally:
         pipe.stdout.close()
         pipe.stderr.close()