Bug 1394793: remove nslookup calls on download failure; r=aki

History suggests these have been in place for a long time, back to an era when
we used split-horizon DNS and DNS service was flaky.  We don't see this sort of
error very often anymore.

Now we have docker images that do not have nslookup installed, and this is
causing retries to fail.

The other option is to use `socket.getaddrinfo` here, but that introduces new
failure mode and could prevent retries that would otherwise succeed. The least
failure-prone approach is just to remove the calls.

MozReview-Commit-ID: JDjhYxUrROS

UltraBlame original commit: 2f514d66bb019f15d83a51c968ec82fbf42e4443

Author: marco-c

testing/mozharness/external_tools/download_file.py

@@ -40,9 +40,6 @@ def download_file(url, file_name):
         raise
     except urllib2.URLError, e:
         print "URL Error: %s" % url
-        remote_host = urlparse.urlsplit(url)[1]
-        if remote_host:
-            os.system("nslookup %s" % remote_host)
         raise
     except socket.timeout, e:
         print "Timed out accessing %s: %s" % (url, str(e))

testing/mozharness/mozharness/base/script.py

@@ -502,16 +502,6 @@ def _download_file(self, url, file_name):
             if isinstance(e.args[0], OSError) and e.args[0].errno == errno.ENOENT:
                 raise e.args[0]
 
-            remote_host = urlparse.urlsplit(url)[1]
-            if remote_host:
-                nslookup = self.query_exe('nslookup')
-                error_list = [{
-                    'substr': "server can't find %s" % remote_host,
-                    'level': ERROR,
-                    'explanation': "Either %s is an invalid hostname, or DNS is busted." % remote_host,
-                }]
-                self.run_command([nslookup, remote_host],
-                                 error_list=error_list)
             raise
         except socket.timeout, e:
             self.warning("Timed out accessing %s: %s" % (url, str(e)))