cms,tai64,tls_codex,x509-ocsp: use core::error:Error instead of std's Error (#2394)

Author: baloo

cms/src/builder.rs

@@ -83,8 +83,7 @@ pub enum Error {
     Builder(String),
 }
 
-#[cfg(feature = "std")]
-impl std::error::Error for Error {}
+impl core::error::Error for Error {}
 
 impl fmt::Display for Error {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {

tai64/src/lib.rs

@@ -333,8 +333,7 @@ impl fmt::Display for Error {
     }
 }
 
-#[cfg(feature = "std")]
-impl std::error::Error for Error {}
+impl core::error::Error for Error {}
 
 #[cfg(all(test, feature = "std"))]
 mod tests {

tls_codec/src/lib.rs

@@ -104,8 +104,7 @@ pub enum Error {
     LibraryError,
 }
 
-#[cfg(feature = "std")]
-impl std::error::Error for Error {}
+impl core::error::Error for Error {}
 
 impl Display for Error {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {

x509-ocsp/src/builder.rs

@@ -21,8 +21,7 @@ pub enum Error {
     Signature(signature::Error),
 }
 
-#[cfg(feature = "std")]
-impl std::error::Error for Error {}
+impl core::error::Error for Error {}
 
 impl fmt::Display for Error {
     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {