Improve permissions errors

Library/Homebrew/cask/cmd/doctor.rb

@@ -67,7 +67,7 @@ def check_staging_location
 
         if path.exist? && !path.writable?
           add_error "The staging path #{user_tilde(path.to_s)} is not writable by the current user."
-          add_error "To fix, run \'sudo chown -R ${USER}:staff #{user_tilde(path.to_s)}'"
+          add_error "To fix, run \'sudo chown -R $(whoami):staff #{user_tilde(path.to_s)}'"
         end
 
         puts user_tilde(path.to_s)

Library/Homebrew/formula_installer.rb

@@ -289,7 +289,14 @@ def install
       rescue Exception => e # rubocop:disable Lint/RescueException
         # any exceptions must leave us with nothing installed
         ignore_interrupts do
-          formula.prefix.rmtree if formula.prefix.directory?
+          begin
+            formula.prefix.rmtree if formula.prefix.directory?
+          rescue Errno::EACCES, Errno::ENOTEMPTY
+            odie <<~EOS
+              Could not remove #{formula.prefix.basename} keg! Do so manually:
+                sudo rm -rf #{formula.prefix}
+            EOS
+          end
           formula.rack.rmdir_if_possible
         end
         raise if ARGV.homebrew_developer? ||

Library/Homebrew/keg.rb

@@ -310,8 +310,11 @@ def uninstall
     remove_opt_record if optlinked?
     remove_old_aliases
     remove_oldname_opt_record
-  rescue Errno::ENOTEMPTY
-    ofail "Could not remove #{path}! Check its permissions."
+  rescue Errno::EACCES, Errno::ENOTEMPTY
+    odie <<~EOS
+      Could not remove #{name} keg! Do so manually:
+        sudo rm -rf #{path}
+    EOS
   end
 
   def unlink(mode = OpenStruct.new)

Library/Homebrew/reinstall.rb

@@ -45,12 +45,26 @@ def reinstall_formula(f, build_from_source: false)
     ignore_interrupts { restore_backup(keg, keg_was_linked) }
     raise
   else
-    backup_path(keg).rmtree if backup_path(keg).exist?
+    begin
+      backup_path(keg).rmtree if backup_path(keg).exist?
+    rescue Errno::EACCES, Errno::ENOTEMPTY
+      odie <<~EOS
+        Could not remove #{backup_path(keg).parent.basename} backup keg! Do so manually:
+          sudo rm -rf #{backup_path(keg)}
+      EOS
+    end
   end
 
   def backup(keg)
     keg.unlink
-    keg.rename backup_path(keg)
+    begin
+      keg.rename backup_path(keg)
+    rescue Errno::EACCES, Errno::ENOTEMPTY
+      odie <<~EOS
+        Could not rename #{keg.name} keg! Check/fix its permissions:
+          sudo chown -R $(whoami) #{keg}
+      EOS
+    end
   end
 
   def restore_backup(keg, keg_was_linked)

docs/Gems,-Eggs-and-Perl-Modules.md

@@ -116,7 +116,7 @@ If you ever did a `sudo gem`, etc. before then a lot of files will have
 been created owned by root. Fix with:
 
 ```sh
-sudo chown -R $USER /Library/Ruby /Library/Perl /Library/Python
+sudo chown -R $(whoami) /Library/Ruby /Library/Perl /Library/Python
 ```
 
 ## Perl CPAN modules without sudo