Fix error string

[benjeffery]

Typo in error message

[codecov]

Codecov Report

Merging #183 (7cb33ed) into main (1a73c83) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #183   +/-   ##
=======================================
  Coverage   99.77%   99.77%           
=======================================
  Files          12       12           
  Lines         876      876           
  Branches      136      136           
=======================================
  Hits          874      874           
  Partials        2        2           

Flag	Coverage Δ
C	99.77% <ø> (ø)
python	99.77% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

---

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 1a73c83...7cb33ed. Read the comment docs.

[jeromekelleher]

LGTM