diff --git a/common/lib/xmodule/xmodule/static_content.py b/common/lib/xmodule/xmodule/static_content.py
index 6d276fd670..37adc9a46d 100755
--- a/common/lib/xmodule/xmodule/static_content.py
+++ b/common/lib/xmodule/xmodule/static_content.py
@@ -230,6 +230,12 @@ def _write_files(output_root, contents, generated_suffix_map=None):
 
         not_file = not output_file.isfile()
 
+        # Sometimes content is already unicode and sometimes it's not
+        # so we add this conditional here to make sure that below we're
+        # always working with streams of bytes.
+        if not isinstance(file_content, six.binary_type):
+            file_content = file_content.encode('utf-8')
+
         # not_file is included to short-circuit this check, because
         # read_md5 depends on the file already existing
         write_file = not_file or output_file.read_md5() != hashlib.md5(file_content).digest()
diff --git a/tox.ini b/tox.ini
index 388b9e0ae7..628cfa44f4 100644
--- a/tox.ini
+++ b/tox.ini
@@ -61,6 +61,8 @@ passenv =
     XDIST_WORKER_SECURITY_GROUP
     XDIST_WORKER_SUBNET
     PYTHON_VERSION
+    LMS_CFG
+    STUDIO_CFG
 
 deps =
     django111: -r requirements/edx/django.txt