sway/waybar: Make calendar work with special chars

The implementation is not very pretty, but this is a limitation of the
chosen design (parsing the output of a cli tool).

users/simon/modules/sway/waybar.nix

@@ -223,6 +223,7 @@ in
       interval = 300;
       exec = pkgs.writeScript "calendar" /* python */ ''
         #!${pkgs.python3}/bin/python3
+        import html
         import json
         import subprocess
 
@@ -234,7 +235,21 @@ in
 
 
         events_today = khal(["list", "today", "today", "-df", "", "-f", "{title}"]).rstrip().split("\n")
-        events_2d = khal(["list", "today", "tomorrow", "-df", "<b>{name}, {date}</b>"]).rstrip()
+        events_2d = (
+            html.escape(
+                khal(
+                    [
+                        "list",
+                        "today",
+                        "tomorrow",
+                        "-df",
+                        "WAYBARSTARTKHAL{name}, {date}WAYBARENDKHAL",
+                    ]
+                ).rstrip()
+            )
+            .replace("WAYBARSTARTKHAL", "<b>")
+            .replace("WAYBARENDKHAL", "</b>")
+        )
 
         if len(events_today) == 1 and events_today[0] == "No events":
             events_today = []