issue #201: parent: log a warning and work around race for now.

mitogen/parent.py

@@ -26,6 +26,7 @@
 # ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 # POSSIBILITY OF SUCH DAMAGE.
 
+import errno
 import fcntl
 import getpass
 import inspect
@@ -593,7 +594,15 @@ class Stream(mitogen.core.Stream):
             # on_disconnect() call.
             return
 
-        pid, status = os.waitpid(self.pid, os.WNOHANG)
+        try:
+            pid, status = os.waitpid(self.pid, os.WNOHANG)
+        except OSError:
+            e = sys.exc_info()[1]
+            if e.args[0] == errno.ECHILD:
+                LOG.warn('%r: waitpid(%r) produced ECHILD', self.pid, self)
+                return
+            raise
+
         if pid:
             LOG.debug('%r: child process exit status was %d', self, status)
         else: