Add error message notice for missing documentation directory. Fixes #83…

…. (#125)

src/cmd.rs

@@ -1,6 +1,8 @@
+use crate::error::FatalError;
 use cargo::core::shell::Shell;
 use cargo::core::shell::Verbosity::{Normal, Quiet, Verbose};
 use failure::Error;
+use std::path::Path;
 use std::process::Command;
 use termcolor::Color::Green;
 
@@ -9,6 +11,13 @@ use termcolor::Color::Green;
 /// only execute the command if a dry run has not been requested.
 ///
 pub fn call(command: &[&str], path: &str, shell: &mut Shell, dry_run: bool) -> Result<bool, Error> {
+    if !Path::new(path).exists() {
+        return Err(FatalError::DocumentationPathNotPresent {
+            path: path.to_string(),
+        }
+        .into());
+    }
+
     if dry_run {
         shell.status_with_color("", format!("cd {}", path), Green)?;
         shell.status_with_color("", command.join(" "), Green)?;

src/error.rs

@@ -10,4 +10,11 @@ pub enum FatalError {
 
     #[fail(display = "Unknown cargo key found: {}", key)]
     UnknownCargoFileKey { key: String },
+
+    #[fail(
+        display = "Documentation path '{}' not present. \
+                   Was this included as argument to `sphinx-quickstart`?",
+        path
+    )]
+    DocumentationPathNotPresent { path: String },
 }