Fix (command:clean): removes error message 'dir not found' if 'clean' is run multiple times

src/cmd/clean.rs

@@ -3,6 +3,7 @@ use clap::{App, ArgMatches, SubCommand};
 use mdbook::errors::*;
 use mdbook::MDBook;
 use std::fs;
+use std::path::Path;
 
 // Create clap subcommand arguments
 pub fn make_subcommand<'a, 'b>() -> App<'a, 'b> {
@@ -29,7 +30,11 @@ pub fn execute(args: &ArgMatches) -> mdbook::errors::Result<()> {
         Some(dest_dir) => dest_dir.into(),
         None => book.root.join(&book.config.build.build_dir),
     };
+
+    let path_to_dir_to_remove = Path::new(&dir_to_remove);
+    if path_to_dir_to_remove.exists() {
         fs::remove_dir_all(&dir_to_remove).chain_err(|| "Unable to remove the build directory")?;
+    }
 
     Ok(())
 }