provide a more informative message when /usr/local/bin is not writabl…

…e on macOS (#38, #24)

DESCRIPTION

@@ -1,7 +1,7 @@
 Package: tinytex
 Type: Package
 Title: Helper Functions to Install and Maintain 'TeX Live', and Compile 'LaTeX' Documents
-Version: 0.5.3
+Version: 0.5.4
 Authors@R: c(
   person("Yihui", "Xie", role = c("aut", "cre", "cph"), email = "[email protected]", comment = c(ORCID = "0000-0003-0645-5666")),
   person(family = "RStudio, Inc.", role = "cph"),

R/install.R

@@ -96,7 +96,13 @@ install_tinytex = function(
           '--no-admin', '--path', shQuote(repository), if (macos && https) 'tlgpg'
         )
       ))
-      if (res != 0) stop('Failed to install TinyTeX', call. = FALSE)
+      if (res != 0) {
+        if (macos && file.access('/usr/local/bin', 2) != 0) message(
+          'The directory /usr/local/bin is not writable; ',
+          'see https://github.com/yihui/tinytex/issues/24 for more info.'
+        )
+        stop('Failed to install TinyTeX', call. = FALSE)
+      }
       target = normalizePath(
         if (macos) '~/Library/TinyTeX' else '~/.TinyTeX'
       )