Fix failing upgrade message

[rejeep]

If an upgrade fails, there is no dependency to print the name of. Just
print the error message in such case.

[proofit404]

I try to reproduce situation with missing (source gnu):

cask install --debug                                                                                                     ~/.emacs.d
Wrote /home/proofit404/.emacs.d/.cask/24.3.1/elpa/archives/melpa/archive-contents
Debugger entered--Lisp error: (void-variable dependency)
  (error "Dependency %s failed to install: %s\nOutput:\n%s" dependency message output)
  (let ((name (progn (or (and (vectorp (nth 0 data)) (>= (length ...) 8) (memq (aref ... 0) cl-struct-cask-dependency-tags)) (error "%s accessing a non-%s" (quote cask-dependency-name) (quote cask-dependency))) (aref (nth 0 data) 1))) (message (error-message-string (nth 1 data))) (output (nth 2 data))) (error "Dependency %s failed to install: %s\nOutput:\n%s" dependency message output))
  (if (nth 0 data) (let ((name (progn (or (and (vectorp ...) (>= ... 8) (memq ... cl-struct-cask-dependency-tags)) (error "%s accessing a non-%s" (quote cask-dependency-name) (quote cask-dependency))) (aref (nth 0 data) 1))) (message (error-message-string (nth 1 data))) (output (nth 2 data))) (error "Dependency %s failed to install: %s\nOutput:\n%s" dependency message output)) (error "Package installation failed: %s\nOutput:\n%s" message output))
  (let ((data (cdr err))) (if (nth 0 data) (let ((name (progn (or (and ... ... ...) (error "%s accessing a non-%s" ... ...)) (aref (nth 0 data) 1))) (message (error-message-string (nth 1 data))) (output (nth 2 data))) (error "Dependency %s failed to install: %s\nOutput:\n%s" dependency message output)) (error "Package installation failed: %s\nOutput:\n%s" message output)))
  (condition-case err (progn (cask-install (cask-cli--bundle))) (cask-missing-dependencies (let ((missing-dependencies (cdr err))) (error "Some dependencies were not available: %s" (s-join ", " (-map (function symbol-name) (-map (function cask-dependency-name) missing-dependencies)))))) (cask-failed-initialization (let* ((data (cdr err)) (message (error-message-string (nth 0 data))) (output (nth 1 data))) (error "Package initialization failed: %s\nOutput:\n%s" message output))) (cask-failed-installation (let ((data (cdr err))) (if (nth 0 data) (let ((name (progn ... ...)) (message (error-message-string ...)) (output (nth 2 data))) (error "Dependency %s failed to install: %s\nOutput:\n%s" dependency message output)) (error "Package installation failed: %s\nOutput:\n%s" message output)))))
  cask-cli/install()
  commander--handle-command(("install"))
  commander-parse(("install" "--debug"))
  (if commander-parsing-done nil (commander-parse (or commander-args (cdr command-line-args-left))))
  (progn (setq commander-default-config nil) (setq commander-options nil) (setq commander-commands nil) (setq commander-name nil) (setq commander-description nil) (setq commander-default-command nil) (setq commander-no-command nil) (setq commander-parsing-done nil) (-each (quote ((name "cask") (description "Emacs dependency management made easy") (default "install") (command "pkg-file" cask-cli/pkg-file) (command "install" cask-cli/install) (command "update" cask-cli/update) (command "upgrade" cask-cli/upgrade-cask) (command "upgrade-cask" cask-cli/upgrade-cask) (command "exec [*]" cask-cli/exec) (command "init" cask-cli/init) (command "version" cask-cli/version) (command "list" cask-cli/list) (command "info" cask-cli/info) (command "help [command]" cask-cli/help) (command "load-path" cask-cli/load-path) (command "exec-path" cask-cli/exec-path) (command "path" cask-cli/exec-path) (command "package-directory" cask-cli/package-directory) (command "outdated" cask-cli/outdated) (command "files" cask-cli/files) (command "build" cask-cli/build) (command "clean-elc" cask-cli/clean-elc) (command "link [*]" cask-cli/link) (command "package [target-dir]" cask-cli/package) (option "--proxy <host>" cask-cli/cask-proxy) (option "--http-proxy <host>" cask-cli/cask-http-proxy) (option "--https-proxy <host>" cask-cli/cask-https-proxy) (option "--no-proxy" cask-cli/cask-no-proxy) (option "--version" cask-cli/cask-version) (option "-h [command], --help [command]" cask-cli/help) (option "--dev" cask-cli/dev) (option "--debug" cask-cli/debug) (option "--path <path>" cask-cli/set-path) (option "--verbose" cask-cli/verbose))) (function (lambda (form) (cond ((eql (car form) (quote option)) (progn (let* ... ...))) ((eql (car form) (quote command)) (progn (let* ... ...))) ((eql (car form) (quote parse)) (progn (let* ... ... ...))) ((eql (car form) (quote name)) (progn (let* ... ...))) ((eql (car form) (quote description)) (progn (let* ... ...))) ((eql (car form) (quote config)) (progn (let* ... ...))) ((eql (car form) (quote default)) (progn (let* ... ...))) (t (error "Unknown directive: %S" form)))))) (if commander-parsing-done nil (commander-parse (or commander-args (cdr command-line-args-left)))))
  eval-buffer(#<buffer  *load*> nil "/home/proofit404/.local/src/cask/cask-cli.el" nil t)  ; Reading at buffer position 12888
  load-with-code-conversion("/home/proofit404/.local/src/cask/cask-cli.el" "/home/proofit404/.local/src/cask/cask-cli.el" nil t)
  load("/home/proofit404/.local/src/cask/cask-cli.el" nil t t)
  command-line-1(("-scriptload" "/home/proofit404/.local/src/cask/cask-cli.el" "--" "install" "--debug"))
  command-line()
  normal-top-level()