[qa] Use python2/3 syntax

qa/rpc-tests/smartfees.py

@@ -105,7 +105,7 @@ def check_estimates(node, fees_seen, max_invalid, print_estimates = True):
         print([str(all_estimates[e-1]) for e in [1,2,3,6,15,25]])
     delta = 1.0e-6 # account for rounding error
     last_e = max(fees_seen)
-    for e in filter(lambda x: x >= 0, all_estimates):
+    for e in [x for x in all_estimates if x >= 0]:
         # Estimates should be within the bounds of what transactions fees actually were:
         if float(e)+delta < min(fees_seen) or float(e)-delta > max(fees_seen):
             raise AssertionError("Estimated fee (%f) out of range (%f,%f)"