How to debug collision between elpy and htmlize during org-export

Question

Description

Below I include

• a minimal Emacs init file
• a minimal org file

Attempting to export the org file to HTML (by using C-c C-e h h) results in the error Wrong type argument: processp, nil. A full debugger backtrace is included at the bottom.

This error can be made to disappear by removing any single one of the following three items:

1. (use-package elpy)
2. (use-package htmlize)
3. The source block from the org file.

How can I resolve this problem?

Details

Configuration:

• Emacs 25.1.1
• Org mode 8.2.10
• elpy 20180406.217
• htmlize 20180328.2341
• use-package 20180314.1143

$HOME/.emacs.d/init.el:

(require 'package)
(setq package-enable-at-startup nil)
(add-to-list 'package-archives '("melpa"     . "http://melpa.org/packages/"))
(add-to-list 'package-archives '("gnu"       . "http://elpa.gnu.org/packages/"))
(package-initialize)

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

(eval-when-compile
  (require 'use-package))

(setq use-package-always-ensure t)
(put 'use-package 'lisp-indent-function 1)

(use-package org
  :config
  (require 'ox-html) ;; Hack around backends not appearing in export dispatcher
  (require 'ox-latex))

(use-package htmlize)

(use-package elpy)


(custom-set-variables
 ;; custom-set-variables was added by Custom.
 ;; If you edit it by hand, you could mess it up, so be careful.
 ;; Your init file should contain only one such instance.
 ;; If there is more than one, they won't work right.
 '(package-selected-packages (quote (elpy htmlize use-package))))
(custom-set-faces
 ;; custom-set-faces was added by Custom.
 ;; If you edit it by hand, you could mess it up, so be careful.
 ;; Your init file should contain only one such instance.
 ;; If there is more than one, they won't work right.
 )

Org file

#+BEGIN_SRC shell
# comment
echo "string" > file
#+END_SRC

Debugger output

Debugger entered--Lisp error: (wrong-type-argument processp nil)
  process-command(nil)
  shell-mode()
  org-html-fontify-code("# comment\necho \"string\" > file\n" "shell")
  org-html-do-format-code("# comment\necho \"string\" > file\n" "shell" nil t nil)
  org-html-format-code((src-block (:language "shell" :switches nil :parameters nil :begin 1 :end 60 :number-lines nil :preserve-indent nil :retain-labels t :use-labels t :label-fmt nil :hiddenp nil :value "# comment\necho \"string\" > file\n" :post-blank 0 :post-affiliated 1 :parent (section (:begin 1 :end 60 :contents-begin 1 :contents-end 60 :post-blank 0 :parent (org-data nil #2)) #0))) (:export-options nil :input-file "/home/jacek/DELETEME/emacs-htmlize-org-export-disaster/.emacs.d/testing.org" :input-buffer "testing.org" :html-extension "html" :html-link-org-as-html t :html-doctype "xhtml-strict" :html-container "div" :html-html5-fancy nil :html-link-use-abs-url nil :html-link-home "" :html-link-up "" :html-mathjax "" :html-postamble auto :html-preamble t :html-head "" :html-head-extra "" :html-head-include-default-style t :html-head-include-scripts t :html-table-attributes (:border "2" :cellspacing "0" :cellpadding "6" :rules "groups" :frame "hsides") :html-table-row-tags ("<tr>" . "</tr>") :html-xml-declaration (("html" . "<?xml version=\"1.0\" encoding=\"%s\"?>") ("php" . "<?php echo \"<?xml version=\\\"1.0\\\" encoding=\\\"%s\\\" ?>\"; ?>")) :html-inline-images t :infojs-opt nil :creator "<a href=\"http://www.gnu.org/software/emacs/\">Emacs</a> 25.1.1 (<a href=\"http://orgmode.org\">Org</a> mode 8.2.10)" :with-latex t ...))
  org-html-src-block((src-block (:language "shell" :switches nil :parameters nil :begin 1 :end 60 :number-lines nil :preserve-indent nil :retain-labels t :use-labels t :label-fmt nil :hiddenp nil :value "# comment\necho \"string\" > file\n" :post-blank 0 :post-affiliated 1 :parent (section (:begin 1 :end 60 :contents-begin 1 :contents-end 60 :post-blank 0 :parent (org-data nil #2)) #0))) nil (:export-options nil :input-file "/home/jacek/DELETEME/emacs-htmlize-org-export-disaster/.emacs.d/testing.org" :input-buffer "testing.org" :html-extension "html" :html-link-org-as-html t :html-doctype "xhtml-strict" :html-container "div" :html-html5-fancy nil :html-link-use-abs-url nil :html-link-home "" :html-link-up "" :html-mathjax "" :html-postamble auto :html-preamble t :html-head "" :html-head-extra "" :html-head-include-default-style t :html-head-include-scripts t :html-table-attributes (:border "2" :cellspacing "0" :cellpadding "6" :rules "groups" :frame "hsides") :html-table-row-tags ("<tr>" . "</tr>") :html-xml-declaration (("html" . "<?xml version=\"1.0\" encoding=\"%s\"?>") ("php" . "<?php echo \"<?xml version=\\\"1.0\\\" encoding=\\\"%s\\\" ?>\"; ?>")) :html-inline-images t :infojs-opt nil :creator "<a href=\"http://www.gnu.org/software/emacs/\">Emacs</a> 25.1.1 (<a href=\"http://orgmode.org\">Org</a> mode 8.2.10)" :with-latex t ...))
  org-export-data((src-block (:language "shell" :switches nil :parameters nil :begin 1 :end 60 :number-lines nil :preserve-indent nil :retain-labels t :use-labels t :label-fmt nil :hiddenp nil :value "# comment\necho \"string\" > file\n" :post-blank 0 :post-affiliated 1 :parent (section (:begin 1 :end 60 :contents-begin 1 :contents-end 60 :post-blank 0 :parent (org-data nil #2)) #0))) (:export-options nil :input-file "/home/jacek/DELETEME/emacs-htmlize-org-export-disaster/.emacs.d/testing.org" :input-buffer "testing.org" :html-extension "html" :html-link-org-as-html t :html-doctype "xhtml-strict" :html-container "div" :html-html5-fancy nil :html-link-use-abs-url nil :html-link-home "" :html-link-up "" :html-mathjax "" :html-postamble auto :html-preamble t :html-head "" :html-head-extra "" :html-head-include-default-style t :html-head-include-scripts t :html-table-attributes (:border "2" :cellspacing "0" :cellpadding "6" :rules "groups" :frame "hsides") :html-table-row-tags ("<tr>" . "</tr>") :html-xml-declaration (("html" . "<?xml version=\"1.0\" encoding=\"%s\"?>") ("php" . "<?php echo \"<?xml version=\\\"1.0\\\" encoding=\\\"%s\\\" ?>\"; ?>")) :html-inline-images t :infojs-opt nil :creator "<a href=\"http://www.gnu.org/software/emacs/\">Emacs</a> 25.1.1 (<a href=\"http://orgmode.org\">Org</a> mode 8.2.10)" :with-latex t ...))
  #[(element) "\302    \"\207" [element info org-export-data] 3]((src-block (:language "shell" :switches nil :parameters nil :begin 1 :end 60 :number-lines nil :preserve-indent nil :retain-labels t :use-labels t :label-fmt nil :hiddenp nil :value "# comment\necho \"string\" > file\n" :post-blank 0 :post-affiliated 1 :parent (section (:begin 1 :end 60 :contents-begin 1 :contents-end 60 :post-blank 0 :parent (org-data nil #2)) #0))))
  mapconcat(#[(element) "\302  \"\207" [element info org-export-data] 3] ((src-block (:language "shell" :switches nil :parameters nil :begin 1 :end 60 :number-lines nil :preserve-indent nil :retain-labels t :use-labels t :label-fmt nil :hiddenp nil :value "# comment\necho \"string\" > file\n" :post-blank 0 :post-affiliated 1 :parent (section (:begin 1 :end 60 :contents-begin 1 :contents-end 60 :post-blank 0 :parent (org-data nil #3)) #1)))) "")
  org-export-data((section (:begin 1 :end 60 :contents-begin 1 :contents-end 60 :post-blank 0 :parent (org-data nil #0)) (src-block (:language "shell" :switches nil :parameters nil :begin 1 :end 60 :number-lines nil :preserve-indent nil :retain-labels t :use-labels t :label-fmt nil :hiddenp nil :value "# comment\necho \"string\" > file\n" :post-blank 0 :post-affiliated 1 :parent #0))) (:export-options nil :input-file "/home/jacek/DELETEME/emacs-htmlize-org-export-disaster/.emacs.d/testing.org" :input-buffer "testing.org" :html-extension "html" :html-link-org-as-html t :html-doctype "xhtml-strict" :html-container "div" :html-html5-fancy nil :html-link-use-abs-url nil :html-link-home "" :html-link-up "" :html-mathjax "" :html-postamble auto :html-preamble t :html-head "" :html-head-extra "" :html-head-include-default-style t :html-head-include-scripts t :html-table-attributes (:border "2" :cellspacing "0" :cellpadding "6" :rules "groups" :frame "hsides") :html-table-row-tags ("<tr>" . "</tr>") :html-xml-declaration (("html" . "<?xml version=\"1.0\" encoding=\"%s\"?>") ("php" . "<?php echo \"<?xml version=\\\"1.0\\\" encoding=\\\"%s\\\" ?>\"; ?>")) :html-inline-images t :infojs-opt nil :creator "<a href=\"http://www.gnu.org/software/emacs/\">Emacs</a> 25.1.1 (<a href=\"http://orgmode.org\">Org</a> mode 8.2.10)" :with-latex t ...))
  #[(element) "\302    \"\207" [element info org-export-data] 3]((section (:begin 1 :end 60 :contents-begin 1 :contents-end 60 :post-blank 0 :parent (org-data nil #0)) (src-block (:language "shell" :switches nil :parameters nil :begin 1 :end 60 :number-lines nil :preserve-indent nil :retain-labels t :use-labels t :label-fmt nil :hiddenp nil :value "# comment\necho \"string\" > file\n" :post-blank 0 :post-affiliated 1 :parent #0))))
  mapconcat(#[(element) "\302  \"\207" [element info org-export-data] 3] ((section (:begin 1 :end 60 :contents-begin 1 :contents-end 60 :post-blank 0 :parent (org-data nil #1)) (src-block (:language "shell" :switches nil :parameters nil :begin 1 :end 60 :number-lines nil :preserve-indent nil :retain-labels t :use-labels t :label-fmt nil :hiddenp nil :value "# comment\necho \"string\" > file\n" :post-blank 0 :post-affiliated 1 :parent #1)))) "")
  org-export-data((org-data nil (section (:begin 1 :end 60 :contents-begin 1 :contents-end 60 :post-blank 0 :parent #0) (src-block (:language "shell" :switches nil :parameters nil :begin 1 :end 60 :number-lines nil :preserve-indent nil :retain-labels t :use-labels t :label-fmt nil :hiddenp nil :value "# comment\necho \"string\" > file\n" :post-blank 0 :post-affiliated 1 :parent #1)))) (:export-options nil :input-file "/home/jacek/DELETEME/emacs-htmlize-org-export-disaster/.emacs.d/testing.org" :input-buffer "testing.org" :html-extension "html" :html-link-org-as-html t :html-doctype "xhtml-strict" :html-container "div" :html-html5-fancy nil :html-link-use-abs-url nil :html-link-home "" :html-link-up "" :html-mathjax "" :html-postamble auto :html-preamble t :html-head "" :html-head-extra "" :html-head-include-default-style t :html-head-include-scripts t :html-table-attributes (:border "2" :cellspacing "0" :cellpadding "6" :rules "groups" :frame "hsides") :html-table-row-tags ("<tr>" . "</tr>") :html-xml-declaration (("html" . "<?xml version=\"1.0\" encoding=\"%s\"?>") ("php" . "<?php echo \"<?xml version=\\\"1.0\\\" encoding=\\\"%s\\\" ?>\"; ?>")) :html-inline-images t :infojs-opt nil :creator "<a href=\"http://www.gnu.org/software/emacs/\">Emacs</a> 25.1.1 (<a href=\"http://orgmode.org\">Org</a> mode 8.2.10)" :with-latex t ...))
  org-export-as(html nil nil nil (:output-file "./testing.html"))
  org-export-to-file(html "./testing.html" nil nil nil nil nil)
  org-html-export-to-html(nil nil nil nil)
  org-export-dispatch(nil)
  funcall-interactively(org-export-dispatch nil)
  call-interactively(org-export-dispatch nil nil)
  command-execute(org-export-dispatch)

Answer 1

There is no obvious link with elpy package in your settings. Two small modifications of your code seems to be needed:

1. In your org file you need: #+BEGIN_SRC sh only.
2. In your init file, you need to add: (require 'ob-sh) to org configuration.

Then the html file is generated without problems. I suggest also to upgrade to org 9.x