Fix next(), print(), and raw_input() to work in both Python 2 and Python 3 (#5599)

Legacy print statements are syntax errors in Python 3 but print() function works as expected in both Python 2 and Python 3.

Resolves syntax errors and name errors that have the potential to halt the runtime.

Risk Level: Minimal
Testing: http://flake8.pycqa.org

Signed-off-by: cclauss <cclauss@me.com>

Mirrored from https://github.com/envoyproxy/envoy @ abd82f7c078b5c38faaecb885b46e0ac053e0353

tools/capture2pcap.py

@@ -17,6 +17,7 @@ issue.
 TODO(htuch):
 - Figure out IPv6 PCAP issue above, or file a bug once the root cause is clear.
 """
+from __future__ import print_function
 
 import datetime
 import socket
@@ -81,6 +82,6 @@ def Capture2Pcap(capture_path, pcap_path):
 
 if __name__ == '__main__':
   if len(sys.argv) != 3:
-    print 'Usage: %s <capture .pb/.pb_text> <pcap path>' % sys.argv[0]
+    print('Usage: %s <capture .pb/.pb_text> <pcap path>' % sys.argv[0])
     sys.exit(1)
   Capture2Pcap(sys.argv[1], sys.argv[2])

tools/capture2pcap_test.py

@@ -1,4 +1,5 @@
 """Tests for capture2pcap."""
+from __future__ import print_function
 
 import os
 import subprocess as sp
@@ -20,7 +21,7 @@ if __name__ == '__main__':
   with open(expected_path, 'r') as f:
     expected_output = f.read()
   if actual_output != expected_output:
-    print 'Mismatch'
-    print 'Expected: %s' % expected_output
-    print 'Actual: %s' % actual_output
+    print('Mismatch')
+    print('Expected: %s' % expected_output)
+    print('Actual: %s' % actual_output)
     sys.exit(1)

tools/generate_listeners.py

@@ -47,7 +47,7 @@ def GenerateListeners(listeners_pb_path, output_pb_path, output_json_path, fragm
 
   for filter_chain in listener.filter_chains:
     for f in filter_chain.filters:
-      f.config.CopyFrom(ProtoToStruct(ParseProto(fragments.next(), f.name)))
+      f.config.CopyFrom(ProtoToStruct(ParseProto(next(fragments), f.name)))
 
   with open(output_pb_path, 'w') as f:
     f.write(str(listener))