constantify the override filename
diff --git a/server/plugins/ldap.py b/server/plugins/ldap.py
index 70c5fac..ecfcbe5 100644
--- a/server/plugins/ldap.py
+++ b/server/plugins/ldap.py
@@ -18,6 +18,7 @@
 import os
 
 UID_RE = re.compile(r"^(?:uid=)?([^,]+)")
+PROJECTS_OVERRIDE = "projects.yaml"
 
 
 class LDAPConfig:
@@ -43,7 +44,7 @@
     connection: typing.Optional[bonsai.LDAPConnection]
     ldap_override: dict
 
-    def __init__(self, config: LDAPConfig, ldap_override_yaml="projects.yaml"):
+    def __init__(self, config: LDAPConfig, ldap_override_yaml=PROJECTS_OVERRIDE):
         self.config = config
         self.client = None
         self.connection = None