Installed black from apt.

.emacs.d/init.el

@@ -18,12 +18,6 @@
 (server-start)
 (setq exec-path (append exec-path '("/home/mdk/.local/bin")))
 
-(setenv "PATH"  ; This is so blacken-mode can find black in ~/.local/bin/
-        (concat
-         (getenv "PATH") path-separator
-         (getenv "HOME") "/.local/bin/"
-         ))
-
 (setq package-archives '(("gnu" . "https://elpa.gnu.org/packages/")
                          ("org" . "https://orgmode.org/elpa/")
                          ("melpa" . "https://melpa.org/packages/")))

README.md

@@ -20,6 +20,7 @@ Then add sid (for firefox, at least):
 ```bash
 apt install \
     bash-completion \
+    black \
     dnsutils \
     ecryptfs-utils \
     emacs-gtk \