Ensure /proc/net/ can be pulled for ListeningPortsTest

Bug: 201010504
Change-Id: I9914e38be8a954c7488268955a506dccdbaa4a0d
diff --git a/hostsidetests/appsecurity/src/android/appsecurity/cts/ListeningPortsTest.java b/hostsidetests/appsecurity/src/android/appsecurity/cts/ListeningPortsTest.java
index 3e78032..cfd0b8b 100644
--- a/hostsidetests/appsecurity/src/android/appsecurity/cts/ListeningPortsTest.java
+++ b/hostsidetests/appsecurity/src/android/appsecurity/cts/ListeningPortsTest.java
@@ -232,7 +232,8 @@
      */
     private String parse(String procFilePath) throws IOException, DeviceNotAvailableException {
         File procFile = File.createTempFile("ListeningPortsTest", "tmp");
-        getDevice().pullFile(procFilePath, procFile);
+        boolean result = getDevice().pullFile(procFilePath, procFile);
+        assertTrue("failed to pull " + procFilePath, result);
         procFile.deleteOnExit();
 
         Scanner scanner = null;