Weird random failure in testbugfix, on IsDocumentedWord( "d" );

[fingolfin]

It started on PR #2385: in the first few builds I saw a very strange failure in testbugfix, but couldn't reproduce it locally, on both macOS and a Ubuntu system. This is the failure:

########> Diff in /home/travis/build/gap-system/gap/tst/testbugfix/2012-07-13-\
t00248.tst:2
# Input is:
IsDocumentedWord( "d" );
# Expected output:
false
# But found:
Error, no method found! For debugging hints type ?Recovery from NoMethodFound
Error, no 1st choice method found for `SplitString' on 3 arguments

The initial version of the PR passed. Then it failed three times; the final version again passed. But note that the first FAIL was after a rebase; the final success also was after a pure rebase.

• PASS: Build #6335
• FAIL: Build #6342
• FAIL: Build #6347
• FAIL: Build #6354
• PASS: Build #6380

UPDATE: Besides the first one, it now appeared on several more builds:

• Job #6424.10 for PR Make types returned by NEW_TYPE immutable #2395
• Job #6431.10 for PR Change #include <src/foo.h> to #include "foo.h" #2412
• Job #6434.10 for PR kernel: remove S_PARTIALFLOAT1, mark float parsing hack #2416
• Job #6435.10 for PR kernel: use C99 init for streams' StructInitInfo #2417
• Job #6437.10 for PR Overview of changes in GAP 4.9.1 release #2418

So something really bad is going on here...

[fingolfin]

Note that master builds so far were not affected. And I still can't reproduce it locally. A bad case of a Heisenbug :-(