Improve exception message for invalid image view names

[gsteel]

Fixes #182

[codecov]

Codecov Report

Merging #185 (4b57af0) into 1.2.x (1fae8ac) will increase coverage by 1.67%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##              1.2.x     #185      +/-   ##
============================================
+ Coverage     92.59%   94.26%   +1.67%     
  Complexity      666      666              
============================================
  Files            51       51              
  Lines          1714     1779      +65     
============================================
+ Hits           1587     1677      +90     
+ Misses          127      102      -25     

Impacted Files	Coverage Δ
src/Exception/ImageViewNotFound.php	100.00% <100.00%> (ø)
src/Predicate.php	100.00% <0.00%> (ø)
src/Api.php	96.36% <0.00%> (+15.15%)	⬆️

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