Merge pull request #1503 from vodik/travis-py37

Add python 3.7-dev to travis, allow it to fail

.travis.yml

@@ -5,8 +5,12 @@ python:
   - "3.4"
   - "3.5"
   - "3.6"
+  - "3.7-dev"
   - pypy
   - pypy3
+matrix:
+  allow_failures:
+    - python: "3.7-dev"
 install:
   - pip install -r requirements-travis.txt
   - pip install -e .

hy/_compat.py

@@ -23,6 +23,7 @@ import sys
 PY3 = sys.version_info[0] >= 3
 PY35 = sys.version_info >= (3, 5)
 PY36 = sys.version_info >= (3, 6)
+PY37 = sys.version_info >= (3, 7)
 
 str_type     = str   if PY3 else unicode      # NOQA
 bytes_type   = bytes if PY3 else str          # NOQA

hy/importer.py

@@ -18,7 +18,7 @@ import inspect
 import os
 import __future__
 
-from hy._compat import PY3, MAGIC, builtins, long_type, wr_long
+from hy._compat import PY3, PY37, MAGIC, builtins, long_type, wr_long
 from hy._compat import string_types
 
 
@@ -220,6 +220,12 @@ def write_code_as_pyc(fname, code):
 
     with builtins.open(cfile, 'wb') as fc:
         fc.write(MAGIC)
+        if PY37:
+            # With PEP 552, the header structure has a new flags field
+            # that we need to fill in. All zeros preserve the legacy
+            # behaviour, but should we implement reproducible builds,
+            # this is where we'd add the information.
+            wr_long(fc, 0)
         wr_long(fc, timestamp)
         if PY3:
             wr_long(fc, st.st_size)