BUG: Fix escape character

[larsoner]

Not sure if you'd prefer a r string instead, but this fixes the char warning on nibabel import for me.

[codecov]

Codecov Report

Merging #909 into master will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master     #909      +/-   ##
==========================================
- Coverage   91.73%   91.73%   -0.01%     
==========================================
  Files          97       97              
  Lines       12359    12359              
  Branches     2177     2177              
==========================================
- Hits        11338    11337       -1     
  Misses        684      684              
- Partials      337      338       +1     

Impacted Files	Coverage Δ
nibabel/cifti2/cifti2.py	96.67% <ø> (ø)
nibabel/volumeutils.py	83.94% <0.00%> (-0.20%)	⬇️

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[matthew-brett]

Really sorry - but would you consider an r string instead?

[larsoner]

No problem, done!

[matthew-brett]

Thanks - that's quick ...