URL checker tweaks

• 44b5ac47 test_urls: Ensure status is set despite exceptions
• 76aee60a test_urls: Skip lavaphabbridge.apertis.org since it's slow
• c63cc838 test_urls: Skip the internal Phabricator tasks
• 51feffc5 test_urls: Print timings
• 0109ab04 test_urls: Collect broken URLs in a list
• 64b65730 test_urls: Summarize the broken URLs at the end

added 9 commits

• 64b65730...0667a454 - 3 commits from branch master
• ba95764f - test_urls: Ensure status is set despite exceptions
• 03e0936f - test_urls: Skip lavaphabbridge.apertis.org since it's slow
• d5330388 - test_urls: Skip the internal Phabricator tasks
• 91549fbb - test_urls: Print timings
• 0284ba94 - test_urls: Collect broken URLs in a list
• 3357d560 - test_urls: Summarize the broken URLs at the end

Compare with previous version

requested review from @martyn

merged