strange errors with latest snapshot

[Julien Cubizolles <j.cubizolles@free.fr>]

I'm using the emacs-shapshot packages from the ubuntu-elisp team at
launchpad.net. Since the latest upgrade (package
20170313:93220-84b6bc9-emacs-25.1~ubuntu17.04.1, GNU Emacs 26.0.50
(build 2, x86_64-pc-linux-gnu, GTK+ Version 3.20.9) of 2017-03-14) I
noticed two strange (and very annoying errors):

+ pdf-tools doesn't display pdfs anymore, complaining with

--8<---------------cut here---------------start------------->8---
Error during redisplay: (eval (number-to-string (pdf-cache-number-of-pages))) signaled (file-error "Setting current directory" "Permission non accordée" "~")--8<---------------cut here---------------end--------------->8---

+ several packages can't be upgraded by package.el (yasnippet, pdf-tools
for instance), the error messages are:

--8<---------------cut here---------------start------------->8---
Package transaction finished. mar. 14 mars 2017 18:34:40 CET
Errors:
  (error Package does not untar cleanly into directory yasnippet-20170310.1724/)
--8<---------------cut here---------------end--------------->8---

What might be causing this ?

Julien.