tests: adjust import/export test for python 3

tests/test_import_export.py

@@ -9,6 +9,7 @@ import pytest
 from django.contrib.auth.models import Group
 from django.core.files import File
 from django.core.management import call_command
+from django.utils.encoding import force_bytes
 from django.utils.six import BytesIO, StringIO
 
 from combo.apps.assets.models import Asset
@@ -37,12 +38,12 @@ def some_map_layers():
 
 @pytest.fixture
 def some_assets():
-    Asset(key='banner', asset=File(StringIO('test'), 'test.png')).save()
-    Asset(key='favicon', asset=File(StringIO('test2'), 'test2.png')).save()
+    Asset(key='banner', asset=File(BytesIO(b'test'), 'test.png')).save()
+    Asset(key='favicon', asset=File(BytesIO(b'test2'), 'test2.png')).save()
 
 def get_output_of_command(command, *args, **kwargs):
     old_stdout = sys.stdout
-    output = sys.stdout = BytesIO()
+    output = sys.stdout = StringIO()
     call_command(command, *args, **kwargs)
     sys.stdout = old_stdout
     return output.getvalue()
@@ -67,7 +68,7 @@ def test_import_export(app, some_data):
     assert Page.objects.count() == 0
 
     with tempfile.NamedTemporaryFile() as f:
-        f.write(output)
+        f.write(force_bytes(output))
         f.flush()
         call_command('import_site', f.name)
 
@@ -109,7 +110,7 @@ def test_import_export_map_layers(app, some_map_layers):
     assert MapLayer.objects.count() == 0
 
     with tempfile.NamedTemporaryFile() as f:
-        f.write(output)
+        f.write(force_bytes(output))
         f.flush()
         call_command('import_site', f.name)
 
@@ -189,7 +190,7 @@ def test_import_export_assets(app, some_assets):
     assert Asset.objects.count() == 0
 
     with tempfile.NamedTemporaryFile() as f:
-        f.write(output)
+        f.write(force_bytes(output))
         f.flush()
         call_command('import_site', f.name)