Launch jobs with variable nice value

Description

Based on the discussion in https://git.xfel.eu/calibration/planning/-/issues/110, this MR introduces a flexible --nice value passed to sbatch depending on the number of jobs running in the selected partition for this instrument. Originally only meant for active proposals, the code is cleaner when just using the partition value determined before and is currently changed by ITDM's script anyway shortly after submission. I will clarify this point before merging.

How Has This Been Tested?

Tests! Unit tests!

Types of changes

• New feature (non-breaking change which adds functionality)

Reviewers

@roscar @kluyvert @ahmedk

webservice/webservice.py

@@ -695,10 +695,12 @@ async def get_slurm_nice(partition: str, instrument: str,
     """
 
     # List all names for jobs running in the specified partition.
-    code, job_names = await run_proc_async(
+    returncode, job_names = await run_proc_async(
         ['squeue', '-h', '-o', '%.20j', '-p', partition, '--me'])
 
-    if code != 0:
+    if returncode != 0:
+        logging.error(f'Non-zero return code {returncode} from '
+                      f'`squeue` upon counting number of jobs')
         return 0  # Fallback if something went wrong.
 
     # Base value depending on proposal type using cycle, assuming that