beaker: patch for easier debugging of function locks

pkgs/patch-beaker-lock-func-debug.diff

@@ -0,0 +1,20 b''
+diff -rup Beaker-1.9.1-orig/beaker/container.py Beaker-1.9.1/beaker/container.py
+--- Beaker-1.9.1-orig/beaker/container.py	2018-04-10 10:23:04.000000000 +0200
++++ Beaker-1.9.1/beaker/container.py	2018-04-10 10:23:34.000000000 +0200
+@@ -353,13 +353,13 @@ class Value(object):
+                 debug("get_value returning old value while new one is created")
+                 return value
+             else:
+-                debug("lock_creatfunc (didnt wait)")
++                debug("lock_creatfunc `%s` (didnt wait)", self.createfunc.__name__)
+                 has_createlock = True
+
+         if not has_createlock:
+-            debug("lock_createfunc (waiting)")
++            debug("lock_createfunc `%s` (waiting)", self.createfunc.__name__)
+             creation_lock.acquire()
+-            debug("lock_createfunc (waited)")
++            debug("lock_createfunc `%s` (waited)", self.createfunc.__name__)
+
+         try:
+             # see if someone created the value already

pkgs/python-packages-overrides.nix

@@ -12,6 +12,12 b' in'
 
 self: super: {
 
+  Beaker = super.Beaker.override (attrs: {
+    patches = [
+      ./patch-beaker-lock-func-debug.diff
+    ];
+  });
+
   subvertpy = super.subvertpy.override (attrs: {
     # TODO: johbo: Remove the "or" once we drop 16.03 support
     SVN_PREFIX = "${pkgs.subversion.dev or pkgs.subversion}";