judgeenv: parse arguments outside of try

[Riolku]

Although it's nonsense to spawn a judge without a model_file, it's also nonsense to parse these args in this try, because it leads to useless error messages.

Specifically, the judge name and key show up as None.

[codecov-commenter]

Codecov Report

Merging #1026 (80b65ac) into master (9551b06) will increase coverage by 2.94%. The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #1026      +/-   ##
==========================================
+ Coverage   81.24%   84.19%   +2.94%     
==========================================
  Files         140      140              
  Lines        4789     4789              
==========================================
+ Hits         3891     4032     +141     
+ Misses        898      757     -141     

Impacted Files	Coverage Δ
dmoj/judgeenv.py	56.84% <ø> (ø)
dmoj/judge.py	53.98% <0.00%> (+1.22%)	:arrow_up:
dmoj/executors/java_executor.py	85.35% <0.00%> (+2.02%)	:arrow_up:
dmoj/cptbox/compiler_isolate.py	55.31% <0.00%> (+6.38%)	:arrow_up:
dmoj/cptbox/tracer.py	76.32% <0.00%> (+18.02%)	:arrow_up:
dmoj/cptbox/handlers.py	100.00% <0.00%> (+26.31%)	:arrow_up:
dmoj/cptbox/isolate.py	89.63% <0.00%> (+38.41%)	:arrow_up:
dmoj/control.py	100.00% <0.00%> (+64.70%)	:arrow_up:

---

Continue to review full report at Codecov.

Legend - Click here to learn more Δ = absolute <relative> (impact), ø = not affected, ? = missing data Powered by Codecov. Last update 9551b06...80b65ac. Read the comment docs.

[kiritofeng]

Implemented as part of #728.