bitcoin: Move consensus_validation module errors to error submodule

diff --git a/bitcoin/src/consensus_validation.rs b/bitcoin/src/consensus_validation.rs
index 9ac9e804..7dad714c 100644
--- a/bitcoin/src/consensus_validation.rs
+++ b/bitcoin/src/consensus_validation.rs
@@ -4,11 +4,6 @@
 //!
 //! Relies on the `bitcoinconsensus` crate that uses Bitcoin Core libconsensus to perform validation.
 
-use core::convert::Infallible;
-use core::fmt;
-
-use internals::write_err;
-
 use crate::amount::Amount;
 use crate::consensus::encode;
 #[cfg(doc)]
@@ -17,6 +12,10 @@ use crate::internal_macros::define_extension_trait;
 use crate::script::ScriptPubKey;
 use crate::transaction::{OutPoint, Transaction, TxOut};
 
+#[rustfmt::skip]                // Keep public re-exports separate.
+#[doc(no_inline)]
+pub use self::error::{BitcoinconsensusError, TxVerifyError};
+
 /// Verifies spend of an input script.
 ///
 /// Shorthand for [`consensus_validation::verify_script_with_flags`] with flag
@@ -207,62 +206,72 @@ mod sealed {
     impl Sealed for super::Transaction {}
 }
 
-/// Wrapped error from `bitcoinconsensus`.
-// We do this for two reasons:
-// 1. We don't want the error to be part of the public API because we do not want to expose the
-//    unusual versioning used in `bitcoinconsensus` to users of `rust-bitcoin`.
-// 2. We want to implement `std::error::Error` if the "std" feature is enabled in `rust-bitcoin` but
-//    not in `bitcoinconsensus`.
-#[derive(Debug, Clone, PartialEq, Eq)]
-#[non_exhaustive]
-pub struct BitcoinconsensusError(bitcoinconsensus::Error);
+/// Error types for consensus validation
+pub mod error {
+    use core::convert::Infallible;
+    use core::fmt;
+
+    use internals::write_err;
+
+    use crate::transaction::OutPoint;
 
-impl fmt::Display for BitcoinconsensusError {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write_err!(f, "bitcoinconsensus error"; &self.0)
+    /// Wrapped error from `bitcoinconsensus`.
+    // We do this for two reasons:
+    // 1. We don't want the error to be part of the public API because we do not want to expose the
+    //    unusual versioning used in `bitcoinconsensus` to users of `rust-bitcoin`.
+    // 2. We want to implement `std::error::Error` if the "std" feature is enabled in `rust-bitcoin` but
+    //    not in `bitcoinconsensus`.
+    #[derive(Debug, Clone, PartialEq, Eq)]
+    #[non_exhaustive]
+    pub struct BitcoinconsensusError(pub(super) bitcoinconsensus::Error);
+
+    impl fmt::Display for BitcoinconsensusError {
+        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+            write_err!(f, "bitcoinconsensus error"; &self.0)
+        }
     }
-}
 
-#[cfg(feature = "bitcoinconsensus")]
-#[cfg(feature = "std")]
-impl std::error::Error for BitcoinconsensusError {
-    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> { Some(&self.0) }
-}
+    #[cfg(feature = "bitcoinconsensus")]
+    #[cfg(feature = "std")]
+    impl std::error::Error for BitcoinconsensusError {
+        fn source(&self) -> Option<&(dyn std::error::Error + 'static)> { Some(&self.0) }
+    }
 
-/// An error during transaction validation.
-#[derive(Debug, Clone, PartialEq, Eq)]
-#[non_exhaustive]
-pub enum TxVerifyError {
-    /// Error validating the script with bitcoinconsensus library.
-    ScriptVerification(BitcoinconsensusError),
-    /// Cannot find the spent output.
-    UnknownSpentOutput(OutPoint),
-}
+    /// An error during transaction validation.
+    #[derive(Debug, Clone, PartialEq, Eq)]
+    #[non_exhaustive]
+    pub enum TxVerifyError {
+        /// Error validating the script with bitcoinconsensus library.
+        ScriptVerification(BitcoinconsensusError),
+        /// Cannot find the spent output.
+        UnknownSpentOutput(OutPoint),
+    }
 
-impl From<Infallible> for TxVerifyError {
-    fn from(never: Infallible) -> Self { match never {} }
-}
+    impl From<Infallible> for TxVerifyError {
+        fn from(never: Infallible) -> Self { match never {} }
+    }
 
-impl fmt::Display for TxVerifyError {
-    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        match self {
-            Self::ScriptVerification(ref e) =>
-                write_err!(f, "bitcoinconsensus verification failed"; e),
-            Self::UnknownSpentOutput(ref p) => write!(f, "unknown spent output: {}", p),
+    impl fmt::Display for TxVerifyError {
+        fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+            match self {
+                Self::ScriptVerification(ref e) =>
+                    write_err!(f, "bitcoinconsensus verification failed"; e),
+                Self::UnknownSpentOutput(ref p) => write!(f, "unknown spent output: {}", p),
+            }
         }
     }
-}
 
-#[cfg(feature = "std")]
-impl std::error::Error for TxVerifyError {
-    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
-        match self {
-            Self::ScriptVerification(ref e) => Some(e),
-            Self::UnknownSpentOutput(_) => None,
+    #[cfg(feature = "std")]
+    impl std::error::Error for TxVerifyError {
+        fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
+            match self {
+                Self::ScriptVerification(ref e) => Some(e),
+                Self::UnknownSpentOutput(_) => None,
+            }
         }
     }
-}
 
-impl From<BitcoinconsensusError> for TxVerifyError {
-    fn from(e: BitcoinconsensusError) -> Self { Self::ScriptVerification(e) }
+    impl From<BitcoinconsensusError> for TxVerifyError {
+        fn from(e: BitcoinconsensusError) -> Self { Self::ScriptVerification(e) }
+    }
 }