Bump dnspython from 2.3.0 to 2.4.2 (#2123)

* Bump dnspython from 2.3.0 to 2.4.2

Bumps [dnspython](https://github.com/rthalley/dnspython) from 2.3.0 to 2.4.2.
- [Release notes](https://github.com/rthalley/dnspython/releases)
- [Changelog](https://github.com/rthalley/dnspython/blob/master/doc/whatsnew.rst)
- [Commits](https://github.com/rthalley/dnspython/compare/v2.3.0...v2.4.2)

---
updated-dependencies:
- dependency-name: dnspython
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

* Update dnspython==2.4.2

---------

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: JonnyWong16 <9099342+JonnyWong16@users.noreply.github.com>

[skip ci]

lib/dns/dnssecalgs/cryptography.py

@@ -0,0 +1,68 @@
+from typing import Any, Optional, Type
+
+from cryptography.hazmat.primitives import serialization
+
+from dns.dnssecalgs.base import GenericPrivateKey, GenericPublicKey
+from dns.exception import AlgorithmKeyMismatch
+
+
+class CryptographyPublicKey(GenericPublicKey):
+    key: Any = None
+    key_cls: Any = None
+
+    def __init__(self, key: Any) -> None:  # pylint: disable=super-init-not-called
+        if self.key_cls is None:
+            raise TypeError("Undefined private key class")
+        if not isinstance(  # pylint: disable=isinstance-second-argument-not-valid-type
+            key, self.key_cls
+        ):
+            raise AlgorithmKeyMismatch
+        self.key = key
+
+    @classmethod
+    def from_pem(cls, public_pem: bytes) -> "GenericPublicKey":
+        key = serialization.load_pem_public_key(public_pem)
+        return cls(key=key)
+
+    def to_pem(self) -> bytes:
+        return self.key.public_bytes(
+            encoding=serialization.Encoding.PEM,
+            format=serialization.PublicFormat.SubjectPublicKeyInfo,
+        )
+
+
+class CryptographyPrivateKey(GenericPrivateKey):
+    key: Any = None
+    key_cls: Any = None
+    public_cls: Type[CryptographyPublicKey]
+
+    def __init__(self, key: Any) -> None:  # pylint: disable=super-init-not-called
+        if self.key_cls is None:
+            raise TypeError("Undefined private key class")
+        if not isinstance(  # pylint: disable=isinstance-second-argument-not-valid-type
+            key, self.key_cls
+        ):
+            raise AlgorithmKeyMismatch
+        self.key = key
+
+    def public_key(self) -> "CryptographyPublicKey":
+        return self.public_cls(key=self.key.public_key())
+
+    @classmethod
+    def from_pem(
+        cls, private_pem: bytes, password: Optional[bytes] = None
+    ) -> "GenericPrivateKey":
+        key = serialization.load_pem_private_key(private_pem, password=password)
+        return cls(key=key)
+
+    def to_pem(self, password: Optional[bytes] = None) -> bytes:
+        encryption_algorithm: serialization.KeySerializationEncryption
+        if password:
+            encryption_algorithm = serialization.BestAvailableEncryption(password)
+        else:
+            encryption_algorithm = serialization.NoEncryption()
+        return self.key.private_bytes(
+            encoding=serialization.Encoding.PEM,
+            format=serialization.PrivateFormat.PKCS8,
+            encryption_algorithm=encryption_algorithm,
+        )