frappe: fix python premailer dependency

premailer.premailer.ExternalFileLoadingError: Unable to load external
file 'assets/frappe/dist/css/email.bundle.HETZ7G4Y.css' because it's
explicitly not allowed

Unsupported new option introduced in premailer version 3.9.0
allow_loading_external_files=False
https://github.com/peterbe/premailer/blob/master/CHANGES.rst#390

Also, sort dependencies in python overlay by usage

python-overlay.nix

@@ -5,23 +5,35 @@ final: prev: {
       erpnext = pyFinal.callPackage ./python/erpnext.nix {};
       frappe = pyFinal.callPackage ./python/frappe.nix {};
 
+      # bench dependencies
+      honcho = pyFinal.callPackage ./python/honcho.nix {};
+
+      # erpnext dependencies
+      gocardless-pro = pyFinal.callPackage ./python/gocardless-pro.nix {};
+      python-youtube = pyFinal.callPackage ./python/python-youtube.nix {};
+      redisearch = pyFinal.callPackage ./python/redisearch.nix {};
+      taxjar = pyFinal.callPackage ./python/taxjar.nix {};
+
+      # frappe dependencies
       email-reply-parser = pyFinal.callPackage ./python/email-reply-parser.nix {};
       git-url-parse = pyFinal.callPackage ./python/git-url-parse.nix {};
-      gocardless-pro = pyFinal.callPackage ./python/gocardless-pro.nix {};
-      honcho = pyFinal.callPackage ./python/honcho.nix {};
-      jsonobject = pyFinal.callPackage ./python/jsonobject.nix {};
       maxminddb-geolite2 = pyFinal.callPackage ./python/maxminddb-geolite2.nix {};
       posthog = pyFinal.callPackage ./python/posthog.nix {};
+      premailer = pyFinal.callPackage ./python/premailer.nix {};
       psycopg2-binary = pyFinal.callPackage ./python/psycopg2-binary.nix {};
       pypdf2 = pyFinal.callPackage ./python/pypdf2.nix {};
       pypika = pyFinal.callPackage ./python/pypika.nix {};
-      python-youtube = pyFinal.callPackage ./python/python-youtube.nix {};
       rauth = pyFinal.callPackage ./python/rauth.nix {};
-      redisearch = pyFinal.callPackage ./python/redisearch.nix {};
-      rejson = pyFinal.callPackage ./python/rejson.nix {};
-      taxjar = pyFinal.callPackage ./python/taxjar.nix {};
       traceback-with-variables = pyFinal.callPackage ./python/traceback-with-variables.nix {};
 
+      # indirect dependencies
+      # taxjar
+      jsonobject = pyFinal.callPackage ./python/jsonobject.nix {};
+      # redisearch
+      rejson = pyFinal.callPackage ./python/rejson.nix {};
+
+
+
       bleach = pyPrev.bleach.overridePythonAttrs (oldAttrs: (rec {
         version = "3.3.1";
         src = pyPrev.fetchPypi {

python/frappe.nix

@@ -115,7 +115,6 @@ buildPythonPackage rec {
     "openpyxl"
     "phonenumbers"
     "Pillow"
-    "premailer"
     "pyasn1"
     "pycountry"
     "pycryptodome"

python/premailer.nix

@@ -0,0 +1,22 @@
+{ buildPythonPackage
+, fetchPypi
+, cssselect
+, cssutils
+, lxml
+, mock
+, nose
+, requests
+, cachetools
+}:
+buildPythonPackage rec {
+  pname = "premailer";
+  version = "3.8.0";
+
+  buildInputs = [ mock nose ];
+  propagatedBuildInputs = [ cachetools cssselect cssutils lxml requests ];
+
+  src = fetchPypi {
+    inherit pname version;
+    sha256 = "sha256-TU4VckTO6UWgDBT+qp5qOusvryYj/2qLoIr99QX6DyU=";
+  };
+}