tests: Fix regex complaints by python3

Signed-off-by: Donald Sharp <sharpd@nvidia.com>

tests/topotests/bgp_multiview_topo1/test_bgp_multiview_topo1.py

@@ -169,7 +169,7 @@ def test_bgp_converge():
         for i in range(1, 2):
             for view in range(1, 4):
                 notConverged = tgen.net["r%s" % i].cmd(
-                    'vtysh -c "show ip bgp view %s summary" 2> /dev/null | grep ^[0-9] | grep -vP " 11\s+(\d+)"'
+                    r'vtysh -c "show ip bgp view %s summary" 2> /dev/null | grep ^[0-9] | grep -vP " 11\s+(\d+)"'
                     % view
                 )
                 if notConverged:

tests/topotests/bgp_srv6l3vpn_to_bgp_vrf/test_bgp_srv6l3vpn_to_bgp_vrf.py

@@ -41,7 +41,7 @@ pytestmark = [pytest.mark.bgpd]
 
 
 def build_topo(tgen):
-    """
+    r"""
       CE1     CE3      CE5
     (eth0)  (eth0)   (eth0)
       :2      :2      :2

tests/topotests/ospf6_ecmp_inter_area/test_ospf6_ecmp_inter_area.py

@@ -21,7 +21,7 @@
 # OF THIS SOFTWARE.
 #
 
-"""
+r"""
 test_ospf6_ecmp_inter_area.py: Test OSPFv3 ECMP inter-area nexthop update
 
 Check proper removal of ECMP nexthops after a path used by one nexthop

tests/topotests/route_scale/scale_test_common.py

@@ -158,7 +158,7 @@ def route_install_helper(iter):
 
     # Avoid top ecmp case for runs with < 4G memory
     output = tgen.net.cmd_raises("free")
-    m = re.search("Mem:\s+(\d+)\s+(\d+)\s+(\d+)\s+(\d+)\s+(\d+)\s+(\d+)", output)
+    m = re.search(r"Mem:\s+(\d+)\s+(\d+)\s+(\d+)\s+(\d+)\s+(\d+)\s+(\d+)", output)
     total_mem = int(m.group(2))
     if total_mem < 4000000 and iter == 5:
         logger.info(