patch 8.2.2905: no error when defaults.vim cannot be loaded

Problem:    No error when defaults.vim cannot be loaded.
Solution:   Add an error message. (Christian Brabandt, closes #8248)
diff --git a/src/testdir/test_startup.vim b/src/testdir/test_startup.vim
index 1f14e86..76060bf 100644
--- a/src/testdir/test_startup.vim
+++ b/src/testdir/test_startup.vim
@@ -276,6 +276,19 @@
    call assert_match("sourcing \"$VIMRUNTIME[\\/]defaults\.vim\"\r\nline 1: \" The default vimrc file\..*  verbose=15\n", out)
 endfunc
 
+" Test that an error is shown when the defaults.vim file could not be read
+func Test_defaults_error()
+  " Can't catch the output of gvim.
+  CheckNotGui
+  CheckNotMSWindows
+
+  let out = system('VIMRUNTIME=/tmp ' .. GetVimCommand() .. ' --clean -cq')
+  call assert_match("E1187: Failed to source defaults.vim", out)
+
+  let out = system('VIMRUNTIME=/tmp ' .. GetVimCommand() .. ' -u DEFAULTS -cq')
+  call assert_match("E1187: Failed to source defaults.vim", out)
+endfunc
+
 " Test the '-q [errorfile]' argument.
 func Test_q_arg()
   CheckFeature quickfix