add from_errno construction to Error

Signed-off-by: Jason Volk <jason@zemos.net>

src/core/error/mod.rs

@@ -131,6 +131,10 @@ pub enum Error {
 }
 
 impl Error {
+	#[inline]
+	#[must_use]
+	pub fn from_errno() -> Self { Self::Io(std::io::Error::last_os_error()) }
+
 	//#[deprecated]
 	pub fn bad_database(message: &'static str) -> Self {
 		crate::err!(Database(error!("{message}")))