[test] Make sys.stdout compatible with both Python 2 & 3

This time's the charm.

llvm-svn: 370552

lldb/packages/Python/lldbsuite/test/lldbpexpect.py

@@ -28,7 +28,8 @@ def expect_prompt(self):
             self.child.expect_exact(self.PROMPT)
 
         def launch(self, executable=None, timeout=30, dimensions=None):
-            logfile = sys.stdout.buffer if self.TraceOn() else None
+            logfile = getattr(sys.stdout, 'buffer',
+                              sys.stdout) if self.TraceOn() else None
             args = ['--no-lldbinit', '--no-use-colors']
             for cmd in self.setUpCommands():
                 args += ['-O', cmd]