build: explain how to test Python 3.6 or 3.7

This helps contributors understand how they can test Python 3.6 or 3.7
on Travis CI.

Helps with issues like:
- #29246 (comment)

.travis.yml

@@ -6,9 +6,13 @@ x-ccache-setup-steps: &ccache-setup-steps
 
 os: linux
 language: cpp
+# Currently this file can only support one PYTHON_VERSION.
+# To experiment with Python 3, comment out Python 2.7 and uncomment one of the Python 3 versions.
 env:
   global:
-    - PYTHON_VERSION="2.7.15"
+    # - PYTHON_VERSION="2.7.15"
+    # - PYTHON_VERSION="3.6.7"
+    - PYTHON_VERSION="3.7.1"
 jobs:
   include:
     - stage: "Compile"

configure

@@ -1,28 +1,34 @@
 #!/bin/sh
 
-# Locate python2 interpreter and re-execute the script.  Note that the
-# mix of single and double quotes is intentional, as is the fact that
-# the ] goes on a new line.
+# Locate an acceptable python interpreter and then re-execute the script.
+# Note that the mix of single and double quotes is intentional,
+# as is the fact that the ] goes on a new line.
+# When a 'which' call is made for a specific version of Python on Travis CI,
+# pyenv will alert which shims are available and then will fail the build.
 _=[ 'exec' '/bin/sh' '-c' '''
+test ${TRAVIS} && exec python "$0" "$@"  # workaround for pyenv on Travis CI
 which python2.7 >/dev/null && exec python2.7 "$0" "$@"
-which python2 >/dev/null && exec python2 "$0" "$@"
+which python3.7 >/dev/null && exec python3.7 "$0" "$@"
+which python3.6 >/dev/null && exec python3.6 "$0" "$@"
+which python3.5 >/dev/null && exec python3.5 "$0" "$@"
 exec python "$0" "$@"
 ''' "$0" "$@"
 ]
 del _
 
 import sys
-from distutils.spawn import find_executable as which
-if sys.version_info[:2] != (2, 7):
-  sys.stderr.write('Please use Python 2.7')
+from distutils.spawn import find_executable
 
-  python2 = which('python2') or which('python2.7')
-
-  if python2:
-    sys.stderr.write(':\n\n')
-    sys.stderr.write('  ' + python2 + ' ' + ' '.join(sys.argv))
-
-  sys.stderr.write('\n')
+print('Node configure: Found Python {0}.{1}.{2}...'.format(*sys.version_info))
+acceptable_pythons = ((2, 7), (3, 7), (3, 6), (3, 5))
+if sys.version_info[:2] in acceptable_pythons:
+  import configure
+else:
+  python_cmds = ['python{0}.{1}'.format(*vers) for vers in acceptable_pythons]
+  sys.stderr.write('Please use {0}.\n'.format(' or '.join(python_cmds)))
+  for python_cmd in python_cmds:
+      python_cmd_path = find_executable(python_cmd)
+      if python_cmd_path and 'pyenv/shims' not in python_cmd_path:
+        sys.stderr.write('\t{0} {1}\n'.format(python_cmd_path,
+                                              ' '.join(sys.argv[:1])))
   sys.exit(1)
-
-import configure

deps/v8/third_party/inspector_protocol/code_generator.py

@@ -43,6 +43,9 @@ def json_object_hook(object_dict):
       items = [(k, os.path.join(output_base, v) if k == "output" else v)
                for (k, v) in items]
       keys, values = list(zip(*items))
+      # 'async' is a Python 3.7+ keyword.  Don't use namedtuple(rename=True)
+      # because that would only rename async on Python 3 but not on Python 2.
+      keys = ['async_' if k == 'async' else k for k in keys]
       return collections.namedtuple('X', keys)(*values)
     return json.loads(data, object_hook=json_object_hook)
 
@@ -555,7 +558,7 @@ def is_async_command(self, domain, command):
     if not self.config.protocol.options:
       return False
     return self.check_options(self.config.protocol.options, domain, command,
-                              "async", None, False)
+                              "async_", None, False)
 
   def is_exported(self, domain, name):
     if not self.config.protocol.options:

tools/inspector_protocol/code_generator.py

@@ -41,6 +41,9 @@ def json_object_hook(object_dict):
             items = [(k, os.path.join(output_base, v) if k == "path" else v) for (k, v) in object_dict.items()]
             items = [(k, os.path.join(output_base, v) if k == "output" else v) for (k, v) in items]
             keys, values = list(zip(*items))
+            # 'async' is a python 3 keyword. Don't use namedtuple(rename=True)
+            # because that only renames it in python 3 but not python 2.
+            keys = tuple('async_' if k == 'async' else k for k in keys)
             return collections.namedtuple('X', keys)(*values)
         return json.loads(data, object_hook=json_object_hook)
 
@@ -521,7 +524,7 @@ def generate_type(self, domain, typename):
     def is_async_command(self, domain, command):
         if not self.config.protocol.options:
             return False
-        return self.check_options(self.config.protocol.options, domain, command, "async", None, False)
+        return self.check_options(self.config.protocol.options, domain, command, "async_", None, False)
 
 
     def is_exported(self, domain, name):