calibre-web: 0.6.12 -> 0.6.13

calibre-web no longer starts without proper calibre DB path configured,
so the default testcase (completely unconfigured) is removed.

(cherry picked from commit 80f7656229efee8817880250b2ca097a69898330)

pkgs/servers/calibre-web/default.nix

@@ -7,13 +7,13 @@
 
 python3.pkgs.buildPythonApplication rec {
   pname = "calibre-web";
-  version = "0.6.12";
+  version = "0.6.13";
 
   src = fetchFromGitHub {
     owner = "janeczku";
     repo = "calibre-web";
     rev = version;
-    sha256 = "sha256-IgS281qDxG302UznC63nZH8/ty4fgFtn+lLYdakGA4w=";
+    sha256 = "sha256-zU7ujvFPi4UaaEglIK3YX3TJxBME35NEKKblnJRt0tM=";
   };
 
   prePatch = ''
@@ -52,6 +52,7 @@ python3.pkgs.buildPythonApplication rec {
     flask_login
     flask_principal
     iso-639
+    lxml
     pypdf3
     requests
     sqlalchemy