use standard lib datetime instead of third party library

Signed-off-by: Kunz, Immanuel <immanuel.kunz@aisec.fraunhofer.de>

Author: immqu

requirements.txt

@@ -3,5 +3,4 @@ packaging==21.0
 pyparsing==2.4.7
 semantic-version==2.8.5
 semver==2.13.0
-isort==5.10.1
-python-dateutil==2.9.0.post0
+isort==5.10.1

setup.cfg

@@ -63,7 +63,6 @@ install_requires =
     packaging
     semantic-version
     semver
-    python-dateutil
 
 
 [options.packages.find]

src/univers/datetime.py

@@ -5,27 +5,31 @@
 
 import re
 
-from dateutil.parser import isoparse
+from datetime import datetime, timezone
 
 
 class DatetimeVersion:
     """
     datetime version.
 
-    The timestamp must be RFC3339-compliant, i.e., a subset of ISO8601, where the date AND time are always specified. Therefore, we can use dateutil's ISO-parser but have to check for compliance with the RFC format first via a regex.
+    The timestamp must be RFC3339-compliant, i.e., a subset of ISO8601, where the date AND time are always specified. Therefore, we cannot use an ISO-parser directly, but have to check for compliance with the RFC format via a regex.
     """
 
     VERSION_PATTERN = re.compile(
         r"^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}(?:\.\d+)?(?:Z|[+-]\d{2}:\d{2})$"
     )
 
     def __init__(self, version):
+        version = str(version).strip()
         if not self.is_valid(version):
             raise InvalidVersionError(version)
 
-        version = str(version).strip()
+        # fromisoformat doesn't accept the "Z" suffix prior to 3.11, so we normalize it:
+        if version.endswith("Z"):
+            version = version[:-1] + "+00:00"
+        
         self.original = version
-        self.parsed_stamp = isoparse(version)
+        self.parsed_stamp = datetime.fromisoformat(version).astimezone(timezone.utc)
 
     def __eq__(self, other):
         return self.parsed_stamp == other.parsed_stamp
@@ -44,7 +48,7 @@ def __ge__(self, other):
 
     @classmethod
     def is_valid(cls, string):
-        return cls.VERSION_PATTERN.match(string)
+        return bool(cls.VERSION_PATTERN.fullmatch(string))
 
 
 class InvalidVersionError(ValueError):

tests/test_version_range.py

@@ -383,6 +383,9 @@ def test_version_range_datetime():
     assert DatetimeVersion("2021-05-05T01:02:03.1234Z") >= DatetimeVersion(
         "2020-05-05T01:02:03.1234Z"
     )
+    assert DatetimeVersion("2021-05-05T01:02:03.1234Z") > DatetimeVersion(
+        "2020-05-05T01:02:03.1234+01:00"
+    )
     assert DatetimeVersion("2000-01-01T01:02:03.1234Z") in DatetimeVersionRange.from_string(
         "vers:datetime/*"
     )