tests/docker: upgrade docker.py to python3

The recent podman changes (9459f75413) imported enum which is part
of the python3 standard library but only available as an external
library for python2. This causes problems on the fairly restricted
environment such as shippable. Lets bite the bullet and make the
script a fully python3 one. To that end:

  - drop the from __future__ import (we are there now ;-)
  - avoid the StringIO import hack
  - be consistent with the mode we read/write dockerfiles
  - s/iteritems/items/
  - ensure check_output returns strings for processing

Signed-off-by: Alex Bennée <alex.bennee@linaro.org>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <philmd@redhat.com>
Cc: Marc-André Lureau <marcandre.lureau@redhat.com>

tests/docker/docker.py

@@ -1,4 +1,4 @@
-#!/usr/bin/env python2
+#!/usr/bin/env python3
 #
 # Docker controlling module
 #
@@ -11,7 +11,6 @@
 # or (at your option) any later version. See the COPYING file in
 # the top-level directory.
 
-from __future__ import print_function
 import os
 import sys
 import subprocess
@@ -25,10 +24,7 @@ import tempfile
 import re
 import signal
 from tarfile import TarFile, TarInfo
-try:
-    from StringIO import StringIO
-except ImportError:
-    from io import StringIO
+from io import StringIO
 from shutil import copy, rmtree
 from pwd import getpwuid
 from datetime import datetime, timedelta
@@ -62,11 +58,13 @@ USE_ENGINE = EngineEnum.AUTO
 
 def _text_checksum(text):
     """Calculate a digest string unique to the text content"""
-    return hashlib.sha1(text).hexdigest()
+    return hashlib.sha1(text.encode('utf-8')).hexdigest()
 
+def _read_dockerfile(path):
+    return open(path, 'rt', encoding='utf-8').read()
 
 def _file_checksum(filename):
-    return _text_checksum(open(filename, 'rb').read())
+    return _text_checksum(_read_dockerfile(filename))
 
 
 def _guess_engine_command():
@@ -192,7 +190,7 @@ def _read_qemu_dockerfile(img_name):
 
     df = os.path.join(os.path.dirname(__file__), "dockerfiles",
                       img_name + ".docker")
-    return open(df, "r").read()
+    return _read_dockerfile(df)
 
 
 def _dockerfile_preprocess(df):
@@ -262,6 +260,7 @@ class Docker(object):
     def _output(self, cmd, **kwargs):
         return subprocess.check_output(self._command + cmd,
                                        stderr=subprocess.STDOUT,
+                                       encoding='utf-8',
                                        **kwargs)
 
     def inspect_tag(self, tag):
@@ -283,7 +282,9 @@ class Docker(object):
         if argv is None:
             argv = []
 
-        tmp_df = tempfile.NamedTemporaryFile(dir=docker_dir, suffix=".docker")
+        tmp_df = tempfile.NamedTemporaryFile(mode="w+t",
+                                             encoding='utf-8',
+                                             dir=docker_dir, suffix=".docker")
         tmp_df.write(dockerfile)
 
         if user:
@@ -396,7 +397,7 @@ class BuildCommand(SubCommand):
                             help="Dockerfile name")
 
     def run(self, args, argv):
-        dockerfile = open(args.dockerfile, "rb").read()
+        dockerfile = _read_dockerfile(args.dockerfile)
         tag = args.tag
 
         dkr = Docker()
@@ -442,7 +443,7 @@ class BuildCommand(SubCommand):
                 cksum += [(filename, _file_checksum(filename))]
 
             argv += ["--build-arg=" + k.lower() + "=" + v
-                     for k, v in os.environ.iteritems()
+                     for k, v in os.environ.items()
                      if k.lower() in FILTERED_ENV_NAMES]
             dkr.build_image(tag, docker_dir, dockerfile,
                             quiet=args.quiet, user=args.user, argv=argv,
@@ -611,7 +612,7 @@ class CheckCommand(SubCommand):
                 print("Need a dockerfile for tag:%s" % (tag))
                 return 1
 
-            dockerfile = open(args.dockerfile, "rb").read()
+            dockerfile = _read_dockerfile(args.dockerfile)
 
             if dkr.image_matches_dockerfile(tag, dockerfile):
                 if not args.quiet: