Emacs lsp-mode save hook call process region issue

demo.py

#!/usr/bin/env python3
#

def main():
    print("foo bar")

Dockerfile

FROM alpine:3.10.1

RUN apk --no-cache add bash emacs python3 py3-setuptools
RUN pip3 install python-language-server black
RUN mkdir -p /root/demo_python_project/.git

COPY dot_emacs /root/.emacs
COPY demo.py /root/demo_python_project/demo.py
CMD /usr/bin/emacs /root/demo_python_project/demo.py

dot_emacs

;; Disable TLS 1.3 due to bug in emacs 26
(setq gnutls-algorithm-priority "NORMAL:-VERS-TLS1.3")

(package-initialize)
(add-to-list 'package-archives
             '("melpa" . "https://melpa.org/packages/")
             )

(when (not package-archive-contents)
  (package-refresh-contents))

(unless (package-installed-p 'use-package)
  (package-install 'use-package))


(defun python-fmt ()
  "Run black."
  (let (
        (originalcolumn (current-column))
        (originalline (count-lines 1 (point)))
        )
    (call-process-region (point-min) (point-max) "black" t t t "--quiet" "--fast" "-")
    (beginning-of-line)
    (with-no-warnings (goto-line originalline))
    (move-to-column originalcolumn)
    )
  (message "Ran black")
  )

(use-package python-mode
  :mode "\\.py\\'"
  :ensure t
  :hook ((python-mode . lsp)
         (python-mode . (lambda () (add-hook 'before-save-hook 'python-fmt nil 'local)))
         )
  )

(use-package lsp-mode
  :ensure t
  :commands lsp
  :config
  (require 'lsp-clients)
  (setq lsp-enable-snippet nil)
  (setq lsp-auto-guess-root t)
  (setq lsp-log-io t)  ;; Log traffic to lsp-log buffer
  (setq lsp-response-timeout 30)
  )

relevant_log

[Trace - 02:45:18 PM] Sending notification 'textDocument/didChange'.
Params: {
  "textDocument": {
    "uri": "file:///root/demo_python_project/demo.py",
    "version": 2
  },
  "contentChanges": [
    {
      "range": {
      	"start": {
          "line": 0,
          "character": 0
        },
        "end": {
          "line": 6,
          "character": 0
        }
      },
      "rangeLength": 60,
      "text": ""
    }
  ]
}