Dependencies: drop the python-dateutil library

This was only used in `aiida.common.timezone.isoformat_to_datetime` and
in the `aiida.restapi.common.utils` module to parse a datetime object
from a string in ISO format. Since Python 3.7 this functionality is
provided in the `datetime` standard library:

    https://docs.python.org/3/library/datetime.html#datetime.datetime.fromisoformat

The only relevant difference between the two implementations is that the
standard library is intentionally strict and will raise for invalid
formats whereas the `python-dateutil` will be lenient and try to guess
the intention in case of invalid formats. For both cases, we prefer not
to guess and potentially guess wrong, so the change is appropriate.

aiida/common/timezone.py

@@ -10,8 +10,6 @@
 """Utility functions to operate on datetime objects."""
 from datetime import datetime
 
-from dateutil import parser
-
 
 def get_current_timezone():
     """Return the current timezone.
@@ -134,6 +132,4 @@ def isoformat_to_datetime(value):
 
     :param value: a ISO format string representation of a datetime object
     """
-    if value is None:
-        return None
-    return parser.parse(value)
+    return datetime.fromisoformat(value) if value is not None else value

aiida/restapi/common/utils.py

@@ -663,8 +663,6 @@ def parse_query_string(self, query_string):
         :param query_string (as obtained from request.query_string)
         :return: parsed values for the querykeys
         """
-
-        from dateutil import parser as dtparser
         from psycopg2.tz import FixedOffsetTimezone
         from pyparsing import Combine, Group, Literal, OneOrMore, Optional, ParseException, QuotedString
         from pyparsing import StringEnd as SE
@@ -722,15 +720,14 @@ def validate_time(toks):
             :param toks: datetime string passed in tokens
             :return: datetime object
             """
-
             datetime_string = toks[0]
 
             # Check the precision
             precision = len(datetime_string.replace('T', ':').split(':'))
 
             # Parse
             try:
-                dtobj = dtparser.parse(datetime_string)
+                dtobj = datetime.fromisoformat(datetime_string)
             except ValueError:
                 raise RestInputValidationError(
                     'time value has wrong format. The '

environment.yml

@@ -27,7 +27,6 @@ dependencies:
 - pgsu~=0.2.1
 - psutil~=5.6
 - psycopg2-binary~=2.8
-- python-dateutil~=2.8
 - pytz~=2021.1
 - pyyaml~=5.4
 - sqlalchemy~=1.4.22

pyproject.toml

@@ -45,7 +45,6 @@ dependencies = [
         "pgsu~=0.2.1",
         "psutil~=5.6",
         "psycopg2-binary~=2.8",
-        "python-dateutil~=2.8",
         "pytz~=2021.1",
         "pyyaml~=5.4",
         "sqlalchemy~=1.4.22",

requirements/requirements-py-3.10.txt

@@ -117,7 +117,6 @@ pytest-datadir==1.3.1
 pytest-regressions==2.2.0
 pytest-rerunfailures==9.1.1
 pytest-timeout==1.4.2
-python-dateutil==2.8.2
 python-memcached==1.59
 pytray==0.3.2
 pytz==2021.3

requirements/requirements-py-3.8.txt

@@ -118,7 +118,6 @@ pytest-datadir==1.3.1
 pytest-regressions==2.2.0
 pytest-rerunfailures==9.1.1
 pytest-timeout==1.4.2
-python-dateutil==2.8.2
 python-memcached==1.59
 pytray==0.3.2
 pytz==2021.3

requirements/requirements-py-3.9.txt

@@ -117,7 +117,6 @@ pytest-datadir==1.3.1
 pytest-regressions==2.2.0
 pytest-rerunfailures==9.1.1
 pytest-timeout==1.4.2
-python-dateutil==2.8.2
 python-memcached==1.59
 pytray==0.3.2
 pytz==2021.3