I put this into /tmp/repro.el:

    (toggle-debug-on-error t)
    (package-initialize)
    (let ((scheme "https://"))
      (setq package-archives
            `(("gnu" . ,(format "%selpa.gnu.org/packages/" scheme))

              ;; More secure; suggested by
https://glyph.twistedmatrix.com/2015/11/editor-malware.html
              ("melpa" . ,(format "%smelpa.org/packages/" scheme))

              ;;
http://blog.jorgenschaefer.de/2014/03/elpy-moves-to-its-own-elpa.html
              ("elpy" . ,(format "%sjorgenschaefer.github.io/packages/"
scheme)))

            tls-checktrust t
            ))
    (package-list-packages)

Then I started emacs with `open --new
~/git-repositories/3rd-party/emacs-master/nextstep/Emacs.app --args -Q
--load /tmp/repro.el`

I saw the *Packages* buffer appear, but the mode line said (Package
Menu:Loading), and stayed that way for many minutes; I expected it to
eventually change to (Package Menu).

I then did M-x list-processes and saw

    elpa.gnu.org    failed   *http elpa.... --           (network
connection to elpa.gnu.org)
    jorgenschaef... failed   *http jorge... --           (network
connection to jorgenschaefer.github.io)
    melpa.org       failed   *http melpa... --           (network
connection to melpa.org)





In GNU Emacs 25.1.50.1 (x86_64-apple-darwin15.3.0, NS appkit-1404.34
Version 10.11.3 (Build 15D21))
 of 2016-03-06 built on Eric-Hanchrows-MacBook-Pro.local
Repository revision: 7882dc625e1ec562fcd0e1b743ef11b160cae18e
Windowing system distributor 'Apple', version 10.3.1404
Configured features:
JPEG RSVG NOTIFY ACL GNUTLS LIBXML2 ZLIB TOOLKIT_SCROLL_BARS NS

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: Package Menu

Minor modes in effect:
  tooltip-mode: t
  global-eldoc-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t
  buffer-read-only: t
  line-number-mode: t
  transient-mark-mode: t

Recent messages:
For information about GNU Emacs and the GNU system, type C-h C-a.
Debug on Error enabled globally
Importing package-keyring.gpg...done
Setting ‘package-selected-packages’ temporarily since "emacs -q" would
overwrite customizations

Load-path shadows:
/Users/erichanchrow/.emacs.d/elpa/helm-20160306.110/helm-multi-match hides
/Users/erichanchrow/.emacs.d/elpa/helm-core-20160305.2327/helm-multi-match
/Users/erichanchrow/.emacs.d/elpa/shorten-20150306.517/shorten hides
/Users/erichanchrow/.emacs.d/elpa/tracking-20151129.319/shorten

Features:
(shadow sort mail-extr emacsbug message dired dired-loaddefs format-spec
rfc822 mml mml-sec epa derived gnus-util rmail rmail-loaddefs mm-decode
mm-bodies mm-encode mailabbrev gmm-utils mailheader sendmail mail-utils
cus-edit wid-edit network-stream nsm starttls url-http tls gnutls
mail-parse rfc2231 rfc2047 rfc2045 mm-util ietf-drums mail-prsvr url-gw
puny seq url-cache url-auth url url-proxy url-privacy url-expand
url-methods url-history url-cookie url-domsuf url-util mailcap epg
finder-inf go-mode-autoloads info package epg-config url-handlers
url-parse auth-source cl-seq eieio byte-opt bytecomp byte-compile
cl-extra help-mode easymenu cconv eieio-core cl-macs gv eieio-loaddefs
cl-loaddefs pcase cl-lib password-cache url-vars cus-start cus-load
time-date mule-util tooltip eldoc electric uniquify ediff-hook vc-hooks
lisp-float-type mwheel term/ns-win ns-win ucs-normalize term/common-win
tool-bar dnd fontset image regexp-opt fringe tabulated-list newcomment
elisp-mode lisp-mode prog-mode register page menu-bar rfn-eshadow timer
select scroll-bar mouse jit-lock font-lock syntax facemenu font-core
term/tty-colors frame cl-generic cham georgian utf-8-lang misc-lang
vietnamese tibetan thai tai-viet lao korean japanese eucjp-ms cp51932
hebrew greek romanian slovak czech european ethiopic indian cyrillic
chinese charscript case-table epa-hook jka-cmpr-hook help simple abbrev
obarray minibuffer cl-preloaded nadvice loaddefs button faces cus-face
macroexp files text-properties overlay sha1 md5 base64 format env
code-pages mule custom widget hashtable-print-readable backquote kqueue
cocoa ns multi-tty make-network-process emacs)

Memory information:
((conses 16 328881 7499)
 (symbols 48 33953 0)
 (miscs 40 61 175)
 (strings 32 51560 10192)
 (string-bytes 1 1213646)
 (vectors 16 39105)
 (vector-slots 8 713983 4934)
 (floats 8 236 111)
 (intervals 56 7211 386)
 (buffers 976 16))