Made valgrind optional. Capture the target output.

Don't fail if valgrind (system version not the google3 one) is missing.
If the test fail, print the output of the test.
Added .pyc to the gitignore file.

testrunner/run_command.py

@@ -145,7 +145,20 @@ def RunHostCommand(binary, valgrind=False):
       print subproc.communicate()[0]
     return subproc.returncode
   else:
+    # Need the full path to valgrind to avoid other versions on the system.
     subproc = subprocess.Popen(["/usr/bin/valgrind", "-q", full_path],
                                stdout=subprocess.PIPE, stderr=subprocess.STDOUT)
     subproc.wait()
     return subproc.returncode
+
+
+def HasValgrind():
+  """Check that /usr/bin/valgrind exists.
+
+  We look for the fullpath to avoid picking up 'alternative' valgrind
+  on the system.
+
+  Returns:
+    True if a system valgrind was found.
+  """
+  return os.path.exists("/usr/bin/valgrind")