Metadata API: remove dateutil requirement

I added "dateutil" as a possible argument type for
`Metadata.bump_expiration()` as we are already testing for this and
implying it should be supported.
The problem is that "dateutil" is not added as a nontest requirement
and after a discussion, we decided we don't want to add it as well.

That's why we decided to remove "dateutil" mentions from the code
and not confuse our users we support it.

We will create a separate issue discussing the validity of
`Metadata.bump_expiration()`.

Signed-off-by: Martin Vrachev <[email protected]>

Author: MVrachev

requirements-test.txt

@@ -3,9 +3,6 @@
 # pinned tuf runtime dependencies (should auto-update and -trigger ci/cd)
 -r requirements-pinned.txt
 
-# tuf.api tests use python-dateutil
-python-dateutil
-
 # additional test tools for linting and coverage measurement
 coverage
 black
@@ -14,4 +11,3 @@ pylint
 mypy
 bandit
 types-requests
-types-python-dateutil

tests/test_api.py

@@ -16,7 +16,6 @@
 from datetime import datetime, timedelta
 from typing import ClassVar, Dict
 
-from dateutil.relativedelta import relativedelta
 from securesystemslib import hash as sslib_hash
 from securesystemslib.interface import (
     import_ed25519_privatekey_from_file,
@@ -333,15 +332,6 @@ def test_metadata_timestamp(self) -> None:
         timestamp.signed.bump_expiration(timedelta(days=365))
         self.assertEqual(timestamp.signed.expires, datetime(2031, 1, 2, 0, 0))
 
-        # Test whether dateutil.relativedelta works, this provides a much
-        # easier to use interface for callers
-        delta = relativedelta(days=1)
-        timestamp.signed.bump_expiration(delta)
-        self.assertEqual(timestamp.signed.expires, datetime(2031, 1, 3, 0, 0))
-        delta = relativedelta(years=5)
-        timestamp.signed.bump_expiration(delta)
-        self.assertEqual(timestamp.signed.expires, datetime(2036, 1, 3, 0, 0))
-
         # Create a MetaFile instance representing what we expect
         # the updated data to be.
         hashes = {

tuf/api/metadata.py

@@ -47,7 +47,6 @@
     cast,
 )
 
-from dateutil.relativedelta import relativedelta
 from securesystemslib import exceptions as sslib_exceptions
 from securesystemslib import hash as sslib_hash
 from securesystemslib import keys as sslib_keys
@@ -501,9 +500,7 @@ def is_expired(self, reference_time: Optional[datetime] = None) -> bool:
         return reference_time >= self.expires
 
     # Modification.
-    def bump_expiration(
-        self, delta: Union[timedelta, relativedelta] = timedelta(days=1)
-    ) -> None:
+    def bump_expiration(self, delta: timedelta = timedelta(days=1)) -> None:
         """Increments the expires attribute by the passed timedelta."""
         self.expires += delta