DOC: Skip creating redirects if docs build fails

[datapythonista]

When the doc build fails, we still try to create the redirected pages, which fails, and adds to the log a misleading error (it looks in the logs like the problem is not the original error but that something is failing in the redirects).

See for example https://travis-ci.org/pandas-dev/pandas/jobs/542714631:

Recursion error: maximum recursion depth exceeded while calling a Python object This can happen with very large or deeply nested source files. You can carefully increase the default Python recursion limit of 1000 in conf.py with e.g.: import sys; sys.setrecursionlimit(1500) Traceback (most recent call last): File "./make.py", line 341, in <module> sys.exit(main()) File "./make.py", line 337, in main return getattr(builder, args.command)() File "./make.py", line 226, in html self._add_redirects() File "./make.py", line 209, in _add_redirects with open(path, 'w') as moved_page_fd: FileNotFoundError: [Errno 2] No such file or directory: '/home/travis/build/pandas-dev/pandas/doc/build/html/generated/pandas.api.extensions.ExtensionArray.argsort.html' 

Here I make the redirects be created only if the doc build succeeded. Also opening the browser if we're building a single page.

[codecov]

Codecov Report

Merging #26752 into master will decrease coverage by 1.41%.
The diff coverage is n/a.

@@ Coverage Diff @@ ## master #26752 +/- ## ========================================== - Coverage 91.7% 90.29% -1.42%  ========================================== Files 179 179 Lines 50767 50767 ========================================== - Hits 46555 45839 -716  - Misses 4212 4928 +716

Flag	Coverage Δ
#multiple	90.29% <ø> (ø)	⬆️
#single	?

Impacted Files	Coverage Δ
pandas/core/computation/pytables.py	62.5% <0%> (-27.75%)	⬇️
pandas/io/pytables.py	63.82% <0%> (-26.48%)	⬇️
pandas/io/gbq.py	78.94% <0%> (-10.53%)	⬇️
pandas/core/computation/common.py	84.21% <0%> (-5.27%)	⬇️
pandas/core/computation/expr.py	94.5% <0%> (-3.03%)	⬇️
pandas/io/clipboard/clipboards.py	31.88% <0%> (-2.9%)	⬇️
pandas/io/formats/printing.py	84.49% <0%> (-1.07%)	⬇️
pandas/core/indexes/datetimes.py	96.21% <0%> (-0.17%)	⬇️
pandas/core/arrays/categorical.py	95.8% <0%> (-0.13%)	⬇️
pandas/core/frame.py	96.88% <0%> (-0.12%)	⬇️

---

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Δ = absolute <relative> (impact), ø = not affected, ? = missing data
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[codecov]

Codecov Report

Merging #26752 into master will decrease coverage by 1.41%.
The diff coverage is n/a.

@@ Coverage Diff @@ ## master #26752 +/- ## ========================================== - Coverage 91.7% 90.29% -1.42%  ========================================== Files 179 179 Lines 50767 50767 ========================================== - Hits 46555 45839 -716  - Misses 4212 4928 +716

Flag	Coverage Δ
#multiple	90.29% <ø> (ø)	⬆️
#single	?

Impacted Files	Coverage Δ
pandas/core/computation/pytables.py	62.5% <0%> (-27.75%)	⬇️
pandas/io/pytables.py	63.82% <0%> (-26.48%)	⬇️
pandas/io/gbq.py	78.94% <0%> (-10.53%)	⬇️
pandas/core/computation/common.py	84.21% <0%> (-5.27%)	⬇️
pandas/core/computation/expr.py	94.5% <0%> (-3.03%)	⬇️
pandas/io/clipboard/clipboards.py	31.88% <0%> (-2.9%)	⬇️
pandas/io/formats/printing.py	84.49% <0%> (-1.07%)	⬇️
pandas/core/indexes/datetimes.py	96.21% <0%> (-0.17%)	⬇️
pandas/core/arrays/categorical.py	95.8% <0%> (-0.13%)	⬇️
pandas/core/frame.py	96.88% <0%> (-0.12%)	⬇️

---

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Legend - Click here to learn more
Δ = absolute <relative> (impact), ø = not affected, ? = missing data
Powered by Codecov. Last update c7748ca...ab4af39. Read the comment docs.

[WillAyd]

Did this error just pop up with a new version of sphinx?

[datapythonista]

Yep, the error was fixed in #26727. This PR is just for future failures of the doc build, to not include the misleading redirects error.

[jreback]

do we already have a good error message to the user if the build fails?

[datapythonista]

yes, we'll have the sphinx error message. In the example in the description, the end of the log will be:

Recursion error: maximum recursion depth exceeded while calling a Python object This can happen with very large or deeply nested source files. You can carefully increase the default Python recursion limit of 1000 in conf.py with e.g.: import sys; sys.setrecursionlimit(1500) 

[jreback]

thanks @datapythonista