[damned-lies] Freeze PyICU version to workaround build failures with 2.4.2

[Claude Paroz <claudep src gnome org>]

commit e7603b138355aa33985b1ed481122cfe8de456a1
Author: Claude Paroz <claude 2xlibre net>
Date:   Sat Nov 23 14:30:53 2019 +0100

    Freeze PyICU version to workaround build failures with 2.4.2

 requirements.txt | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/requirements.txt b/requirements.txt
index 34552923..a3a56711 100644
--- a/requirements.txt
+++ b/requirements.txt
@@ -4,5 +4,5 @@ mysqlclient
 social-auth-app-django==3.1.0
 django-debug-toolbar
 markdown==3.0.1
-pyicu
+pyicu==2.3.1  # 2.4.2 fails to compile on some platforms
 translate-toolkit>=2.2.0