[code coverage] Don't throw exception when handling coverage data failed

Sometimes coverage data might not be generated on device due to wrong configs or tests and command will fail to pull data or remove data.
Don't throw exception so that runner can still print result.

Bug: 843307
Change-Id: Ie08cf676ca1ca2fb0d3ed4a087d31042c0f0a0ba
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1636568Reviewed-by: John Budorick <jbudorick@chromium.org>
Commit-Queue: Yun Liu <yliuyliu@google.com>
Cr-Commit-Position: refs/heads/master@{#664870}

build/android/pylib/local/device/local_device_instrumentation_test_run.py

@@ -13,6 +13,7 @@ import re
 import sys
 import time
 
+from devil import base_error
 from devil.android import crash_handler
 from devil.android import device_errors
 from devil.android import device_temp_file
@@ -577,11 +578,15 @@ class LocalDeviceInstrumentationTestRun(
 
       def handle_coverage_data():
         if self._test_instance.coverage_directory:
+          try:
             device.PullFile(coverage_directory,
                             self._test_instance.coverage_directory)
             device.RunShellCommand(
                 'rm -f %s' % posixpath.join(coverage_directory, '*'),
-              check_return=True, shell=True)
+                check_return=True,
+                shell=True)
+          except base_error.BaseError as e:
+            logging.warning('Failed to handle coverage data after tests: %s', e)
 
       def handle_render_test_data():
         if _IsRenderTest(test):