Revert d39bed41e215, because pty doesn't do the right thing when the process exits, creating a race condition

tools/rb/fix_macosx_stack.py

@@ -146,16 +146,7 @@ def fixSymbols(line):
 
         if os.path.exists(file) and os.path.isfile(file):
             address += address_adjustment(file)
-            try:
-                info = addressToSymbol(file, address)
-                if info.startswith("atos cannot"):
-                    # This can happen due to bug 550335 or bug 558947.
-                    sys.stderr.write("fix_macosx_stack will not convert some stack-trace addresses because: " + info + "\n")
-                    return line
-            except IOError:
-                # IOError can be the result of attempting to continue to use an
-                # atos process that has exited (e.g. due to the error above)
-                return line
+            info = addressToSymbol(file, address)
 
             # atos output seems to have three forms:
             #   address