[libFuzzer] Make DataFlow scripts Python3 compatible.

[Dor1s]

Summary

Python2 will hit end of life soon: https://pythonclock.org/
This change also makes the integration with OSS-Fuzz a bit simpler:
https://github.com/google/oss-fuzz/issues/1632

[Dor1s]

Kostya / Matt, this is fairly minor change, PTAL.

[morehouse]

LGTM

lib/fuzzer/scripts/collect_data_flow.py

-#!/usr/bin/env python
+#!/usr/bin/env python3
 #===- lib/fuzzer/scripts/collect_data_flow.py ------------------------------===#
 #
 # Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 # See https://llvm.org/LICENSE.txt for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 #
 #===------------------------------------------------------------------------===#
 # Runs the data-flow tracer several times on the same input in order to collect

 def collect_dataflow_for_corpus(self, exe, corpus_dir, output_dir):
   print("Collecting dataflow for corpus: %s output_dir: %s" % (corpus_dir,
                                                                output_dir))
   assert not os.path.exists(output_dir)
   os.mkdir(output_dir)
   for root, dirs, files in os.walk(corpus_dir):
     for f in files:
       path = os.path.join(root, f)
-      sha1 = hashlib.sha1(open(path).read()).hexdigest()
+      with open(path, 'rb') as fh:
+        data = fh.read()
+      sha1 = hashlib.sha1(data).hexdigest()
       output = os.path.join(output_dir, sha1)
       subprocess.call([self, exe, path, output])
   functions_txt = open(os.path.join(output_dir, "functions.txt"), "w")
   subprocess.call([exe], stdout=functions_txt)
 
 
 def main(argv):
   exe = argv[1]
   inp = argv[2]
   if os.path.isdir(inp):
     return collect_dataflow_for_corpus(argv[0], exe, inp, argv[3])
   size = os.path.getsize(inp)
   q = [[0, size]]
   tmpdir = tempfile.mkdtemp(prefix="libfuzzer-tmp-")
   atexit.register(cleanup, tmpdir)
-  print "tmpdir: ", tmpdir
+  print("tmpdir: ", tmpdir)
   outputs = []
   while len(q):
     r = q.pop()
-    print "******* Trying:  ", r
+    print("******* Trying:  ", r)
     tmpfile = os.path.join(tmpdir, str(r[0]) + "-" + str(r[1]))
     ret = subprocess.call([exe, str(r[0]), str(r[1]), inp, tmpfile])
     if ret and r[1] - r[0] >= 2:
       q.append([r[0], (r[1] + r[0]) / 2])
       q.append([(r[1] + r[0]) / 2, r[1]])
     else:
       outputs.append(tmpfile)
-      print "******* Success: ", r
+      print("******* Success: ", r)
   f = sys.stdout
   if len(argv) >= 4:
     f = open(argv[3], "w")
   merge = os.path.join(os.path.dirname(argv[0]), "merge_data_flow.py")
   subprocess.call([merge] + outputs, stdout=f)
 
 if __name__ == '__main__':
   main(sys.argv)

lib/fuzzer/scripts/merge_data_flow.py

-#!/usr/bin/env python
+#!/usr/bin/env python3
 #===- lib/fuzzer/scripts/merge_data_flow.py ------------------------------===#
 #
 # Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 # See https://llvm.org/LICENSE.txt for license information.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 #
 #===------------------------------------------------------------------------===#
 # Merge several data flow traces into one.