feat(errors): Use Error trait from core crate

Author: fogti

src/errors.rs

@@ -1,8 +1,7 @@
 use core::fmt::{self, Display, Formatter};
 #[cfg(any(feature = "byte", feature = "bit"))]
 pub use core::num::TryFromIntError;
-#[cfg(feature = "std")]
-use std::error::Error;
+use core::error::Error;
 
 #[cfg(any(feature = "byte", feature = "bit"))]
 use rust_decimal::Decimal;
@@ -21,7 +20,6 @@ impl Display for ExceededBoundsError {
 }
 
 #[cfg(any(feature = "byte", feature = "bit"))]
-#[cfg(feature = "std")]
 impl Error for ExceededBoundsError {}
 
 #[cfg(any(feature = "byte", feature = "bit"))]
@@ -50,7 +48,6 @@ impl Display for ValueParseError {
 }
 
 #[cfg(any(feature = "byte", feature = "bit"))]
-#[cfg(feature = "std")]
 impl Error for ValueParseError {}
 
 /// The error type returned when parsing units.
@@ -111,7 +108,6 @@ impl Display for UnitParseError {
     }
 }
 
-#[cfg(feature = "std")]
 impl Error for UnitParseError {}
 
 #[cfg(any(feature = "byte", feature = "bit"))]
@@ -150,5 +146,4 @@ impl Display for ParseError {
 }
 
 #[cfg(any(feature = "byte", feature = "bit"))]
-#[cfg(feature = "std")]
 impl Error for ParseError {}