Bug 1410723 - Throw DMError when getDirectory() fails suspiciously; r=bc

It looks like the main cause of intermittent failures in getDirectory is
that the adb pull command fails because the emulator has hung. For other
commands, we usually handle this by checking the return code and raising
DMError if anything fails. There is mozharness/taskcluster code in
place to automatically retry tasks that throw DMError.

testing/mozbase/mozdevice/mozdevice/devicemanagerADB.py

@@ -540,14 +540,17 @@ class DeviceManagerADB(DeviceManager):
                 localDir = '/'.join(localDir.rstrip('/').split('/')[:-1])
         cmd = ["pull", remoteDir, localDir]
         proc = self._runCmd(cmd)
+        if proc.returncode != 0:
+            # Raise a DMError when the device is missing, but not when the
+            # directory is empty or missing.
+            if ("no devices/emulators found" in proc.output or
+                ("pulled" not in proc.output and
+                 "does not exist" not in proc.output)):
+                raise DMError("getDirectory() failed to pull %s: %s" %
+                              (remoteDir, proc.output))
         if copyRequired:
-            try:
-                dir_util.copy_tree(localDir, originalLocal)
-                mozfile.remove(tempParent)
-            except:
-                self._logger.error("getDirectory() failed after %s" % str(cmd))
-                self._logger.error("rc=%d out=%s" % (proc.returncode, str(proc.output)))
-                raise
+            dir_util.copy_tree(localDir, originalLocal)
+            mozfile.remove(tempParent)
 
     def validateFile(self, remoteFile, localFile):
         md5Remote = self._getRemoteHash(remoteFile)