Unable to use this mode

[vampolo]

Seems that this mode has problems in starting. in particular i see:

Updating /Users/vampolo/.emacs.d/.cache/quelpa/build/graphviz-dot-mode/
Saving file /Users/vampolo/.emacs.d/.cache/quelpa/packages/graphviz-dot-mode-20160129.34.el...
Wrote /Users/vampolo/.emacs.d/.cache/quelpa/packages/graphviz-dot-mode-20160129.34.el
Wrote /Users/vampolo/.emacs.d/.cache/quelpa/packages/graphviz-dot-mode-readme.txt
Generating autoloads for graphviz-dot-mode.el...done
Wrote /Users/vampolo/.emacs.d/elpa/graphviz-dot-mode-20160129.34/graphviz-dot-mode-autoloads.el
Checking /Users/vampolo/.emacs.d/elpa/graphviz-dot-mode-20160129.34... [3 times]
Compiling /Users/vampolo/.emacs.d/elpa/graphviz-dot-mode-20160129.34/graphviz-dot-mode.el...done
Wrote /Users/vampolo/.emacs.d/elpa/graphviz-dot-mode-20160129.34/graphviz-dot-mode.elc
Checking /Users/vampolo/.emacs.d/elpa/graphviz-dot-mode-20160129.34...
Done (Total of 1 file compiled, 2 skipped)
File mode specification error: (void-variable default-tab-width)
Auto-evilification could not remap these functions in map ‘edebug-mode-map’:
   - ‘edebug-Go-nonstop-mode’ originally mapped on ‘G’
Auto-evilification could not remap these functions in map ‘edebug-mode-map’:
   - ‘edebug-Go-nonstop-mode’ originally mapped on ‘G’
helm-M-x: Symbol’s value as variable is void: default-tab-width

and the mode of my .dot file remains Foundamental.

[shishirsharma]

I too have this issue on mac.

[vnckppl]

Same here (on OSX).

[WallyYang]

This is just telling you that a variable named "default-tab-width" is not set. Simply add
(setq default-tab-wdith 4) or 2 whatever you like somewhere in your config files should fix this

[reidfrasier]

This is just telling you that a variable named "default-tab-width" is not set. Simply add
(setq default-tab-wdith 4) or 2 whatever you like somewhere in your config files should fix this

This fixed the issue.