Address review comments

src/rust/src/x509/extensions.rs

@@ -9,7 +9,6 @@ use crate::error::{CryptographyError, CryptographyResult};
 use crate::x509::{certificate, sct};
 use crate::{types, x509};
 use pyo3::prelude::PyAnyMethods;
-use pyo3::pybacked::PyBackedBytes;
 
 fn encode_general_subtrees<'a>(
     py: pyo3::Python<'a>,
@@ -52,7 +51,7 @@ pub(crate) fn encode_authority_key_identifier<'a>(
     } else {
         None
     };
-    let serial_bytes: PyBackedBytes;
+    let serial_bytes;
     let authority_cert_serial_number =
         if let Some(authority_cert_serial_number) = aki.authority_cert_serial_number {
             serial_bytes = py_uint_to_big_endian_bytes(py, authority_cert_serial_number)?;

src/rust/src/x509/ocsp_req.rs

@@ -171,7 +171,8 @@ fn create_ocsp_request(
     builder: &pyo3::Bound<'_, pyo3::PyAny>,
 ) -> CryptographyResult<OCSPRequest> {
     let builder_request = builder.getattr(pyo3::intern!(py, "_request"))?;
-    let ka = cryptography_keepalive::KeepAlive::new();
+    let serial_number_bytes;
+    //let ka = cryptography_keepalive::KeepAlive::new();
 
     // Declare outside the if-block so the lifetimes are right.
     let (py_cert, py_issuer, py_hash, issuer_name_hash, issuer_key_hash): (
@@ -189,8 +190,8 @@ fn create_ocsp_request(
         (issuer_name_hash, issuer_key_hash, py_serial, py_hash) = builder
             .getattr(pyo3::intern!(py, "_request_hash"))?
             .extract()?;
-        let serial_number_bytes = ka.add(py_uint_to_big_endian_bytes(py, py_serial)?);
-        let serial_number = asn1::BigInt::new(serial_number_bytes).unwrap();
+        serial_number_bytes = py_uint_to_big_endian_bytes(py, py_serial)?;
+        let serial_number = asn1::BigInt::new(&serial_number_bytes).unwrap();
         ocsp::certid_new_from_hash(
             py,
             &issuer_name_hash,