sympy: proper version check

[mloubout]

No description provided.

[codecov]

Codecov Report

Merging #1769 (c598d78) into master (a7d3b38) will decrease coverage by 1.56%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master    #1769      +/-   ##
==========================================
- Coverage   89.47%   87.91%   -1.57%     
==========================================
  Files         208      203       -5     
  Lines       33936    33390     -546     
  Branches     4408     4375      -33     
==========================================
- Hits        30365    29354    -1011     
- Misses       3074     3523     +449     
- Partials      497      513      +16     

Impacted Files	Coverage Δ
devito/finite_differences/elementary.py	94.61% <100.00%> (+0.01%)	⬆️
examples/seismic/acoustic/wavesolver.py	97.29% <100.00%> (-2.71%)	⬇️
tests/test_adjoint.py	26.66% <0.00%> (-73.34%)	⬇️
examples/seismic/tti/operators.py	53.94% <0.00%> (-43.16%)	⬇️
examples/seismic/self_adjoint/operators.py	58.46% <0.00%> (-41.54%)	⬇️
examples/seismic/viscoacoustic/operators.py	59.49% <0.00%> (-40.51%)	⬇️
examples/seismic/elastic/elastic_example.py	47.22% <0.00%> (-30.56%)	⬇️
...mples/seismic/viscoelastic/viscoelastic_example.py	47.22% <0.00%> (-30.56%)	⬇️
examples/seismic/tti/wavesolver.py	68.59% <0.00%> (-29.76%)	⬇️
...les/seismic/viscoacoustic/viscoacoustic_example.py	45.00% <0.00%> (-25.00%)	⬇️
... and 27 more

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[FabioLuporini]

Thanks, approved