DOC: Fix spaces and brackets in ValueError message for option_context.

[pvanmulbregt]

Add a missing space and changed a parenthesis to a bracket in the message of the ValueError raised whenever the args in option_context(*args) don't meet requirements.
'Need to invoke asoption_context(pat, val, [(pat, val), ...)).'
->
'Need to invoke as option_context(pat, val, [(pat, val), ...]).'

• tests added / passed
• passes git diff upstream/master -u -- "*.py" | flake8 --diff

[jbrockmendel]

@pvanmulbregt this looks good, Travis error is unrelated. Can you push again to make it try again?

[pvanmulbregt]

@jbrockmendel: "push again" as in "$ git push -v -f origin"? That tells me "Everything up-to-date". Or did you mean something else?

[jbrockmendel]

That tells me "Everything up-to-date". Or did you mean something else?

Yah, usually I find a or something to fix to get around that.

[codecov]

Codecov Report

Merging #22121 into master will not change coverage.
The diff coverage is 0%.

@@           Coverage Diff           @@
##           master   #22121   +/-   ##
=======================================
  Coverage   92.07%   92.07%           
=======================================
  Files         170      170           
  Lines       50690    50690           
=======================================
  Hits        46672    46672           
  Misses       4018     4018

Flag	Coverage Δ
#multiple	90.48% <0%> (ø)	⬆️
#single	42.31% <0%> (ø)	⬆️

Impacted Files	Coverage Δ
pandas/core/config.py	87.17% <0%> (ø)	⬆️

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[codecov]

Codecov Report

Merging #22121 into master will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##           master   #22121   +/-   ##
=======================================
  Coverage   92.07%   92.07%           
=======================================
  Files         170      170           
  Lines       50690    50690           
=======================================
  Hits        46672    46672           
  Misses       4018     4018

Flag	Coverage Δ
#multiple	90.48% <ø> (ø)	⬆️
#single	42.31% <ø> (ø)	⬆️

Impacted Files	Coverage Δ
pandas/core/config.py	87.17% <ø> (ø)	⬆️

---

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 d30c4a0...52a8210. Read the comment docs.

[jreback]

thanks @pvanmulbregt