[indico-web] Also required

[Andrea Veri <averi src gnome org>]

commit 0a4960a6047cf3876c4610bdb2c37e4843931860
Author: Andrea Veri <av gnome org>
Date:   Tue Jun 29 14:58:13 2021 +0000

    Also required

 static/Dockerfile | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/static/Dockerfile b/static/Dockerfile
index 1b1f935..06e95c1 100644
--- a/static/Dockerfile
+++ b/static/Dockerfile
@@ -1,7 +1,7 @@
 FROM nginxinc/nginx-unprivileged:stable-alpine
 
 USER root
-RUN apk add --no-cache python2 unzip
+RUN apk add --no-cache python2 py3-virtualenv unzip
 
 RUN virtualenv -p /usr/bin/python2 /tmp/indico-venv && \
     source /tmp/indico-venv/bin/activate && \