Replace use of datetime with time.time()

Author: Vasileios Karakasis

unittests/test_schedulers.py

@@ -283,13 +283,13 @@ def test_submit(make_job, exec_ctx):
 def test_submit_timelimit(minimal_job, local_only):
     minimal_job.time_limit = '2s'
     prepare_job(minimal_job, 'sleep 10')
-    t_job = datetime.now()
+    t_job = time.time()
     minimal_job.submit()
     assert minimal_job.jobid is not None
     minimal_job.wait()
-    t_job = datetime.now() - t_job
-    assert t_job.total_seconds() >= 2
-    assert t_job.total_seconds() < 3
+    t_job = time.time() - t_job
+    assert t_job >= 2
+    assert t_job < 3
     with open(minimal_job.stdout) as fp:
         assert re.search('postrun', fp.read()) is None
 
@@ -319,7 +319,7 @@ def test_submit_job_array(make_job, slurm_only, exec_ctx):
 def test_cancel(make_job, exec_ctx):
     minimal_job = make_job(sched_access=exec_ctx.access)
     prepare_job(minimal_job, 'sleep 30')
-    t_job = datetime.now()
+    t_job = time.time()
     minimal_job.submit()
     minimal_job.cancel()
 
@@ -331,9 +331,9 @@ def test_cancel(make_job, exec_ctx):
     time.sleep(0.01)
 
     minimal_job.wait()
-    t_job = datetime.now() - t_job
+    t_job = time.time() - t_job
     assert minimal_job.finished()
-    assert t_job.total_seconds() < 30
+    assert t_job < 30
 
     # Additional scheduler-specific checks
     sched_name = minimal_job.scheduler.registered_name