That looks like an issue with helm-Bibtex. You might try updating it and/or
raise an issue with that package.


On Mon, Apr 3, 2017 at 11:03 AM Johannes Brauer <brauer@nordakademie.de>
wrote:

> that’s what I get executing (require 'org-ref):
>
> Debugger entered--Lisp error: (error "Required feature ‘let-alist’ was not
> provided")
>   require(let-alist)
>
> byte-code("\300\301!\210\300\302!\210\300\303!\210\300\304!\210\300\305!\210\300\306!\210\300\307!\210\300\310!\210\300\311!\207"
> [require bibtex browse-url hl-line ido json url-queue dash let-alist seq] 2)
>   require(biblio-core)
>
> byte-code("\300\301!\210\300\302!\210\300\303!\210\300\304!\210\300\305!\210\300\306!\210\300\307!\210\300\310!\210\311\312!\207"
> [require biblio-core biblio-doi biblio-arxiv biblio-crossref biblio-dblp
> biblio-hal biblio-dissemin biblio-download provide biblio] 2)
>   require(biblio)
>   eval-buffer(#<buffer  *load*-844603> nil
> "/Users/johannes/Library/Preferences/Aquamacs
> Emacs/Packages/elpa/helm-bibtex-20170321.1306/bibtex-completion.el" nil t)
> ; Reading at buffer position 1340
>   load-with-code-conversion("/Users/johannes/Library/Preferences/Aquamacs
> Emacs/Packages/elpa/helm-bibtex-20170321.1306/bibtex-completion.el"
> "/Users/johannes/Library/Preferences/Aquamacs
> Emacs/Packages/elpa/helm-bibtex-20170321.1306/bibtex-completion.el" nil t)
>   require(bibtex-completion)
>   byte-code("\306\307!\210\306\310!\210\306\311!\210\306\312!\210\313
> \314\211  \314  :\203f

-- 
John

-----------------------------------
Professor John Kitchin
Doherty Hall A207F
Department of Chemical Engineering
Carnegie Mellon University
Pittsburgh, PA 15213
412-268-7803
@johnkitchin
http://kitchingroup.cheme.cmu.edu