Make level check stricter

[znicholls]

Pull request

Please confirm that this pull request has done the following:

• [x] Tests added (N/A)
• [x] Documentation added (where applicable) (N/A)
• [x] Example added (either to an existing notebook or as a new notebook, where applicable) (N/A)
• [x] Description in CHANGELOG.rst added
• [x] #331

Adding to CHANGELOG.rst

Please add a single line in the changelog notes similar to one of the following:

- (`#XX <http://link-to-pr.com>`_) Added feature which does something
- (`#XX <http://link-to-pr.com>`_) Fixed bug identified in (`#XX <http://link-to-issue.com>`_)

[znicholls]

Pretty minor but hopefully makes sense @lewisjared

[codecov[bot]]

Codecov Report

Merging #332 (13c9143) into master (c9bdd61) will increase coverage by 0.04%. The diff coverage is 80.00%.

@@            Coverage Diff             @@
##           master     #332      +/-   ##
==========================================
+ Coverage   93.20%   93.25%   +0.04%     
==========================================
  Files          20       20              
  Lines        2591     2594       +3     
  Branches      513      515       +2     
==========================================
+ Hits         2415     2419       +4     
  Misses        111      111              
+ Partials       65       64       -1     

Impacted Files	Coverage Δ
pymagicc/core.py	88.08% <0.00%> (ø)
pymagicc/io/compact.py	87.50% <100.00%> (+0.32%)	:arrow_up:
pymagicc/io/scen.py	97.66% <100.00%> (+0.46%)	:arrow_up:

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[znicholls]

Ignoring codecov