cmd: show cleaner messages, when v can not compile a tool, or update itself

cmd/tools/vself.v

@@ -19,13 +19,18 @@ fn main() {
 		println('V self compiling...')
 	}
 
-	s2 := os.exec(cmd) or { panic(err) }
-	if s2.output.len > 0 {
-		println(s2.output)
-	}
-	if s2.exit_code != 0 {
+	result := os.exec(cmd) or { panic(err) }
+	if result.exit_code != 0 {
+		mut err := 'Permission denied'
+		if !result.output.contains('Permission denied') {
+			err = '\n$result.output'
+		}
+		eprintln('cannot compile to ‘$vroot: $err')
 		exit(1)
 	}
+	if result.output.len > 0 {
+		println(result.output)
+	}
 
 	v_file := if os.user_os() == 'windows' { 'v.exe' } else { 'v' }
 	v2_file := if os.user_os() == 'windows' { 'v2.exe' } else { 'v2' }

cmd/tools/vup.v

@@ -6,14 +6,26 @@ import (
 )
 
 fn main() {
-	println('Updating V...')
 	vroot := os.dir(pref.vexe_path())
 	os.chdir(vroot)
+
+	println('Updating V...')
+
 	// git pull
-	s := os.exec('git pull --rebase origin master') or {
+	git_result := os.exec('git pull --rebase origin master') or {
 		panic(err)
 	}
-	println(s.output)
+
+	if git_result.exit_code != 0 {
+		if git_result.output.contains('Permission denied') {
+			eprintln('have no access ‘$vroot: Permission denied')
+		} else {
+			eprintln(git_result.output)
+		}
+		exit(1)
+	}
+
+	println(git_result.output)
 
 	$if windows {
 		v_backup_file := 'v_old.exe'
@@ -22,14 +34,14 @@ fn main() {
 		}
 		os.mv('v.exe', v_backup_file)
 
-		s2 := os.exec('make.bat') or {
+		make_result := os.exec('make.bat') or {
 			panic(err)
 		}
-		println(s2.output)
+		println(make_result.output)
 	} $else {
-		s2 := os.exec('make') or {
+		make_result := os.exec('make') or {
 			panic(err)
 		}
-		println(s2.output)
+		println(make_result.output)
 	}
 }

vlib/v/util/util.v

@@ -142,7 +142,12 @@ pub fn launch_tool(is_verbose bool, tool_name string) {
 		}
 		tool_compilation := os.exec(compilation_command) or { panic(err) }
 		if tool_compilation.exit_code != 0 {
-			panic('V tool "$tool_source" could not be compiled\n' + tool_compilation.output)
+			mut err := 'Permission denied'
+			if !tool_compilation.output.contains('Permission denied') {
+				err = '\n$tool_compilation.output'
+			}
+			eprintln('cannot compile ‘$tool_source: $err‘')
+			exit(1)
 		}
 	}
 	if is_verbose {