build: add pymemcache dependency

requirements/devstack.txt

@@ -406,6 +406,8 @@ pylint-plugin-utils==0.8.2
     #   -r requirements/local.txt
     #   pylint-celery
     #   pylint-django
+pymemcache==4.0.0
+    # via -r requirements/nonlocal.txt
 pymongo==3.13.0
     # via
     #   -r requirements/local.txt

requirements/monitoring/requirements.txt

@@ -647,6 +647,10 @@ pylint-plugin-utils==0.8.2
     #   -r requirements/monitoring/../test.txt
     #   pylint-celery
     #   pylint-django
+pymemcache==4.0.0
+    # via
+    #   -r requirements/monitoring/../devstack.txt
+    #   -r requirements/monitoring/../production.txt
 pymongo==3.13.0
     # via
     #   -r requirements/monitoring/../devstack.txt

requirements/nonlocal.in

@@ -3,3 +3,4 @@
 
 mysqlclient
 python-memcached
+pymemcache

requirements/nonlocal.txt

@@ -6,6 +6,8 @@
 #
 mysqlclient==2.2.0
     # via -r requirements/nonlocal.in
+pymemcache==4.0.0
+    # via -r requirements/nonlocal.in
 python-memcached==1.59
     # via -r requirements/nonlocal.in
 six==1.16.0

requirements/production.txt

@@ -223,6 +223,8 @@ pyjwt[crypto]==2.8.0
     #   edx-drf-extensions
     #   edx-rest-api-client
     #   social-auth-core
+pymemcache==4.0.0
+    # via -r requirements/nonlocal.txt
 pymongo==3.13.0
     # via
     #   -r requirements/base.txt