diff --git a/common/lib/capa/capa/responsetypes.py b/common/lib/capa/capa/responsetypes.py
index 2f3ede8174..12b7c6db13 100644
--- a/common/lib/capa/capa/responsetypes.py
+++ b/common/lib/capa/capa/responsetypes.py
@@ -2471,7 +2471,7 @@ class CustomResponse(LoncapaResponse):
             msg = msg.replace('<', '<')
 
             # Use etree to prettify the HTML
-            msg = etree.tostring(fromstring_bs(msg), pretty_print=True)
+            msg = etree.tostring(fromstring_bs(msg), pretty_print=True).decode('utf-8')
 
             msg = msg.replace('
', '')
 
diff --git a/common/lib/capa/capa/safe_exec/safe_exec.py b/common/lib/capa/capa/safe_exec/safe_exec.py
index 794fafb3e1..4b62faae08 100644
--- a/common/lib/capa/capa/safe_exec/safe_exec.py
+++ b/common/lib/capa/capa/safe_exec/safe_exec.py
@@ -7,6 +7,7 @@ import hashlib
 from codejail.safe_exec import SafeExecException, json_safe
 from codejail.safe_exec import not_safe_exec as codejail_not_safe_exec
 from codejail.safe_exec import safe_exec as codejail_safe_exec
+import six
 from six import text_type
 
 from . import lazymod
@@ -64,7 +65,7 @@ def update_hash(hasher, obj):
     `obj` in the process.  Only primitive JSON-safe types are supported.
 
     """
-    hasher.update(str(type(obj)))
+    hasher.update(six.b(str(type(obj))))
     if isinstance(obj, (tuple, list)):
         for e in obj:
             update_hash(hasher, e)
@@ -73,7 +74,7 @@ def update_hash(hasher, obj):
             update_hash(hasher, k)
             update_hash(hasher, obj[k])
     else:
-        hasher.update(repr(obj))
+        hasher.update(six.b(repr(obj)))
 
 
 def safe_exec(
@@ -116,7 +117,7 @@ def safe_exec(
     if cache:
         safe_globals = json_safe(globals_dict)
         md5er = hashlib.md5()
-        md5er.update(repr(code))
+        md5er.update(six.b(repr(code)))
         update_hash(md5er, safe_globals)
         key = "safe_exec.%r.%s" % (random_seed, md5er.hexdigest())
         cached = cache.get(key)
diff --git a/common/lib/xmodule/xmodule/capa_base.py b/common/lib/xmodule/xmodule/capa_base.py
index 167df35e7c..52d474cdfb 100644
--- a/common/lib/xmodule/xmodule/capa_base.py
+++ b/common/lib/xmodule/xmodule/capa_base.py
@@ -85,8 +85,8 @@ def randomization_bin(seed, problem_id):
     we'll combine the system's per-student seed with the problem id in picking the bin.
     """
     r_hash = hashlib.sha1()
-    r_hash.update(str(seed))
-    r_hash.update(str(problem_id))
+    r_hash.update(six.b(str(seed)))
+    r_hash.update(six.b(str(problem_id)))
     # get the first few digits of the hash, convert to an int, then mod.
     return int(r_hash.hexdigest()[:7], 16) % NUM_RANDOMIZATION_BINS
 
diff --git a/lms/djangoapps/instructor_task/api_helper.py b/lms/djangoapps/instructor_task/api_helper.py
index 10afaef641..01e9400775 100644
--- a/lms/djangoapps/instructor_task/api_helper.py
+++ b/lms/djangoapps/instructor_task/api_helper.py
@@ -14,6 +14,7 @@ from celery.result import AsyncResult
 from celery.states import FAILURE, READY_STATES, REVOKED, SUCCESS
 from django.utils.translation import ugettext as _
 from opaque_keys.edx.keys import UsageKey
+import six
 from six import text_type
 
 from courseware.courses import get_problems_in_section
@@ -390,7 +391,7 @@ def encode_problem_and_student_input(usage_key, student=None):
         task_key_stub = "_{problem}".format(problem=text_type(usage_key))
 
     # create the key value by using MD5 hash:
-    task_key = hashlib.md5(task_key_stub).hexdigest()
+    task_key = hashlib.md5(six.b(task_key_stub)).hexdigest()
 
     return task_input, task_key