add python 3 compatibility (#60502)

And use django 2.1.

bidon/settings.py

@@ -107,4 +107,5 @@ local_settings_file = os.environ.get(
     'BIDON_SETTINGS_FILE', os.path.join(os.path.dirname(__file__), 'local_settings.py'))
 
 if os.path.exists(local_settings_file):
-    execfile(local_settings_file)
+    with open(local_settings_file) as f:
+        exec(f.read())

setup.py

@@ -25,19 +25,30 @@ class eo_sdist(sdist):
 
 
 def get_version():
+    """Use the VERSION, if absent generates a version with git describe, if not
+    tag exists, take 0.0- and add the length of the commit log.
+    """
     if os.path.exists('VERSION'):
-        version_file = open('VERSION', 'r')
-        version = version_file.read()
-        version_file.close()
-        return version
+        with open('VERSION') as v:
+            return v.read()
     if os.path.exists('.git'):
-        p = subprocess.Popen(['git', 'describe', '--dirty', '--match=v*'], stdout=subprocess.PIPE)
+        p = subprocess.Popen(
+            ['git', 'describe', '--dirty=.dirty', '--match=v*'],
+            stdout=subprocess.PIPE,
+            stderr=subprocess.PIPE,
+        )
         result = p.communicate()[0]
         if p.returncode == 0:
-            version = result.split()[0][1:]
-            version = version.replace('-', '.')
+            result = result.decode('ascii').strip()[1:]  # strip spaces/newlines and initial v
+            if '-' in result:  # not a tagged version
+                real_number, commit_count, commit_hash = result.split('-', 2)
+                version = '%s.post%s+%s' % (real_number, commit_count, commit_hash)
+            else:
+                version = result
             return version
-    return '0'
+        else:
+            return '0.0.post%s' % len(subprocess.check_output(['git', 'rev-list', 'HEAD']).splitlines())
+    return '0.0'
 
 
 class compile_translations(Command):

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 toxworkdir = {env:TMPDIR:/tmp}/tox-{env:USER}/bidon/{env:BRANCH_NAME:}
-envlist = py2-django111-coverage-junit
+envlist = py3-django22-coverage-junit
 
 [testenv]
 usedevelop = True
@@ -11,7 +11,7 @@ setenv =
   coverage: COVERAGE=--cov-report xml --cov-report html --cov=bidon/
   junit: JUNIT=--junitxml=junit-{envname}.xml
 deps =
-  django111: django>=1.11,<1.12
+  django22: django>=2.2,<2.3
   psycopg2<2.9
   pytest-cov
   pytest-django