stop using dict iter* helpers

Change from iter{keys,items,values}() to {keys,items,values}().
Python 3 doesn't offer the iter variants, and we don't really have
any cases where performance is critical where we'd need to avoid
creating the temporary list (which is what Python 2 does).

This is mostly mechanical.

BUG=chromium:980619
TEST=lint is unchanged in chromite
TEST=unittests pass

Change-Id: I591110f2eb5d43bb9268b975b14bd7ade66a4e35
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/chromite/+/1689014
Tested-by: Mike Frysinger <vapier@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Reviewed-by: David Burger <dburger@chromium.org>
diff --git a/scripts/sysmon/net_metrics.py b/scripts/sysmon/net_metrics.py
index e59c8eb..24b6bcd 100644
--- a/scripts/sysmon/net_metrics.py
+++ b/scripts/sysmon/net_metrics.py
@@ -96,7 +96,7 @@
 def _net_io_iter():
   """Generate network IO information."""
   nics = psutil.net_io_counters(pernic=True)
-  for nic, counters in nics.iteritems():
+  for nic, counters in nics.items():
     if _is_virtual_netif(nic):
       continue
     yield nic, counters
@@ -112,7 +112,7 @@
 
 def _collect_net_if_stats():
   """Collect metrics for network interface stats."""
-  for nic, stats in psutil.net_if_stats().iteritems():
+  for nic, stats in psutil.net_if_stats().items():
     if _is_virtual_netif(nic):
       continue
     fields = {'interface': nic}
@@ -132,7 +132,7 @@
 
 def _collect_net_if_addrs():
   """Collects network addresses as metrics."""
-  for nic, addresses in psutil.net_if_addrs().iteritems():
+  for nic, addresses in psutil.net_if_addrs().items():
     if _is_virtual_netif(nic):
       continue
     for address in addresses: