Bump dnspython from 2.6.1 to 2.7.0 (#2440)

* Bump dnspython from 2.6.1 to 2.7.0

Bumps [dnspython](https://github.com/rthalley/dnspython) from 2.6.1 to 2.7.0.
- [Release notes](https://github.com/rthalley/dnspython/releases)
- [Changelog](https://github.com/rthalley/dnspython/blob/main/doc/whatsnew.rst)
- [Commits](https://github.com/rthalley/dnspython/compare/v2.6.1...v2.7.0)

---
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==2.7.0

---------

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/rdata.py

@@ -214,7 +214,7 @@ class Rdata:
         compress: Optional[dns.name.CompressType] = None,
         origin: Optional[dns.name.Name] = None,
         canonicalize: bool = False,
-    ) -> bytes:
+    ) -> None:
         raise NotImplementedError  # pragma: no cover
 
     def to_wire(
@@ -223,14 +223,19 @@ class Rdata:
         compress: Optional[dns.name.CompressType] = None,
         origin: Optional[dns.name.Name] = None,
         canonicalize: bool = False,
-    ) -> bytes:
+    ) -> Optional[bytes]:
         """Convert an rdata to wire format.
 
-        Returns a ``bytes`` or ``None``.
+        Returns a ``bytes`` if no output file was specified, or ``None`` otherwise.
         """
 
         if file:
-            return self._to_wire(file, compress, origin, canonicalize)
+            # We call _to_wire() and then return None explicitly instead of
+            # of just returning the None from _to_wire() as mypy's func-returns-value
+            # unhelpfully errors out with "error: "_to_wire" of "Rdata" does not return
+            # a value (it only ever returns None)"
+            self._to_wire(file, compress, origin, canonicalize)
+            return None
         else:
             f = io.BytesIO()
             self._to_wire(f, compress, origin, canonicalize)
@@ -253,8 +258,9 @@ class Rdata:
 
         Returns a ``bytes``.
         """
-
-        return self.to_wire(origin=origin, canonicalize=True)
+        wire = self.to_wire(origin=origin, canonicalize=True)
+        assert wire is not None  # for mypy
+        return wire
 
     def __repr__(self):
         covers = self.covers()
@@ -434,15 +440,11 @@ class Rdata:
                 continue
             if key not in parameters:
                 raise AttributeError(
-                    "'{}' object has no attribute '{}'".format(
-                        self.__class__.__name__, key
-                    )
+                    f"'{self.__class__.__name__}' object has no attribute '{key}'"
                 )
             if key in ("rdclass", "rdtype"):
                 raise AttributeError(
-                    "Cannot overwrite '{}' attribute '{}'".format(
-                        self.__class__.__name__, key
-                    )
+                    f"Cannot overwrite '{self.__class__.__name__}' attribute '{key}'"
                 )
 
         # Construct the parameter list.  For each field, use the value in
@@ -646,13 +648,14 @@ _rdata_classes: Dict[Tuple[dns.rdataclass.RdataClass, dns.rdatatype.RdataType],
     {}
 )
 _module_prefix = "dns.rdtypes"
+_dynamic_load_allowed = True
 
 
-def get_rdata_class(rdclass, rdtype):
+def get_rdata_class(rdclass, rdtype, use_generic=True):
     cls = _rdata_classes.get((rdclass, rdtype))
     if not cls:
         cls = _rdata_classes.get((dns.rdatatype.ANY, rdtype))
-        if not cls:
+        if not cls and _dynamic_load_allowed:
             rdclass_text = dns.rdataclass.to_text(rdclass)
             rdtype_text = dns.rdatatype.to_text(rdtype)
             rdtype_text = rdtype_text.replace("-", "_")
@@ -670,12 +673,36 @@ def get_rdata_class(rdclass, rdtype):
                     _rdata_classes[(rdclass, rdtype)] = cls
                 except ImportError:
                     pass
-    if not cls:
+    if not cls and use_generic:
         cls = GenericRdata
         _rdata_classes[(rdclass, rdtype)] = cls
     return cls
 
 
+def load_all_types(disable_dynamic_load=True):
+    """Load all rdata types for which dnspython has a non-generic implementation.
+
+    Normally dnspython loads DNS rdatatype implementations on demand, but in some
+    specialized cases loading all types at an application-controlled time is preferred.
+
+    If *disable_dynamic_load*, a ``bool``, is ``True`` then dnspython will not attempt
+    to use its dynamic loading mechanism if an unknown type is subsequently encountered,
+    and will simply use the ``GenericRdata`` class.
+    """
+    # Load class IN and ANY types.
+    for rdtype in dns.rdatatype.RdataType:
+        get_rdata_class(dns.rdataclass.IN, rdtype, False)
+    # Load the one non-ANY implementation we have in CH.  Everything
+    # else in CH is an ANY type, and we'll discover those on demand but won't
+    # have to import anything.
+    get_rdata_class(dns.rdataclass.CH, dns.rdatatype.A, False)
+    if disable_dynamic_load:
+        # Now disable dynamic loading so any subsequent unknown type immediately becomes
+        # GenericRdata without a load attempt.
+        global _dynamic_load_allowed
+        _dynamic_load_allowed = False
+
+
 def from_text(
     rdclass: Union[dns.rdataclass.RdataClass, str],
     rdtype: Union[dns.rdatatype.RdataType, str],