Check for existence of logdog binary and logcat source before uploading.

build/android/test_wrapper/logdog_wrapper.py

Index: build/android/test_wrapper/logdog_wrapper.py
diff --git a/build/android/test_wrapper/logdog_wrapper.py b/build/android/test_wrapper/logdog_wrapper.py
index dea12a97ff7afc1a0fcffe80318a7451426a7d82..bb3f00875bf3b74f0c3237904ca6fa1dde058c85 100755
--- a/build/android/test_wrapper/logdog_wrapper.py
+++ b/build/android/test_wrapper/logdog_wrapper.py
@@ -72,7 +72,16 @@ def main():
                 '-service-account-json', args.service_account_json,
                 'stream', '-source', args.source,
                 '-stream', '-name=%s' % args.name]
-  if os.path.exists(args.logdog_bin_cmd):
+
+  if not os.path.exists(args.logdog_bin_cmd):
+    logging.error(
+        'Logfog binary %s unavailable. Unable to upload logcats.',
+        args.logdog_bin_cmd)
+  elif not os.path.exists(args.source):
+    logging.error(
+        'Logcat sources not found at %s. Unable to upload logcats.',
+        args.source)
+  else:
     subprocess.call(logdog_cmd)
     logging.info('Logcats are located at: %s', url)
   return result