This tessdata path will be included in cpp code by pre-processor macros
https://github.com/ArtifexSoftware/ghostpdl/blob/gs9.54.0/base/tessocr.cpp#L188-L193
Since // is the marker for a comment in cpp and as documented in
https://gcc.gnu.org/onlinedocs/cpp/Stringizing.html "Comments are replaced by
whitespace long before stringizing happens, so they never appear in stringized
text", the STRINGIFY/STRINGIFY2 approach of including a path does not work
when the path contain // , because anything after // is considered a comment
and is not included, causing errors like this when using ghostscript with OCR
in webrunner:

    $ strace -e open -o open.strace /srv/slapgrid/slappart42/srv/runner/shared/ghostscript/4387fe7a8d2034ac5691d43b58134248/bin/gs -sDEVICE=ocr
    GPL Ghostscript 9.54.0 (2021-03-30)
    Copyright (C) 2021 Artifex Software, Inc.  All rights reserved.
    This software is supplied under the GNU AGPLv3 and comes with NO WARRANTY:
    see the file COPYING for details.
    Error opening data file ./eng.traineddata
    Please make sure the TESSDATA_PREFIX environment variable is set to your "tessdata" directory.
    Failed loading language 'eng'
    Tesseract couldn't load any languages!
    **** Unable to open the initial device, quitting.
    $ grep eng open.strace
    open("./eng.traineddata", O_RDONLY)     = -1 ENOENT (No such file or directory)
    open("/srv/slapgrid/slappart42/srv/eng.traineddata", O_RDONLY) = -1 ENOENT (No such file or directory)
    open("eng.traineddata", O_RDONLY)       = -1 ENOENT (No such file or directory)

eng.traineddata is looked up in /srv/slapgrid/slappart42/srv/ because
ghostscript was configured with:

   --with-tessdata=/srv/slapgrid/slappart42/srv//runner//shared/ghostscript/4387fe7a8d2034ac5691d43b58134248/share/tessdata/

and everything after // was stripped.

This was reported upstream as https://bugs.ghostscript.com/show_bug.cgi?id=703905

More about the case of // in slaprunner paths was on commit eb544196
(slparunner: document the reasons why we keep srv//slaprunner, 2019-10-10)

This will be used to do OCR from PDF documents

This version includes an OCR engine based on tesseract.

Also enable shared parts and provide new languages:
Simplied Chinese, Japanese and French

Features:

 * random response is possible of big sizes
 * timeout can be randomized

See merge request nexedi/slapos!979

This fixes 157dd7ab.

It workarounds stack/resilient/pbsready.cfg.in directory:backup string
concatenation:

  backup = $${basedirectory:backup}/$${slap-parameter:namebase}

See merge request !981

This fixes:

  Installing jupyter.
  While:
    Installing jupyter.
    Base installation request: ...
    Getting distribution for 'argon2-cffi'.
  Error: Picked: argon2-cffi = 20.1.0

Addition of argon2-cffi in commit 7d1ea024
was a last-minute change to fix jupyter SR.

Accessing http with path starting with /HTTPS/ would result with 503 responses
from ATS itself.

Test is covering the problem and also asserting that fix does not damage https
access with path starting with /HTTP/

This defers the rendering of `instance-theia.cfg.in` to the instance
creation time instead of the software installation time, which will
allow buildout sections to be added based on the instance parameters.

See merge request !981

Edggetest monitoring got capability of region definition in each cluster.

In order to stabilise parameter serialisation the json-in-xml has been used.

Slave reference can be dangerous for buildout validity or file names.

Request and publication is switched to fully serialised approach, so that
complex data structures like lists and objects can be safely transmitted.

The requests are backward compatible, so for current and simple usage
automatic region is setup.

Much more information are published to main and shared instances, like
lists of available and assigned regions. Regions can be added and removed,
which will be reflected automatically for the slaves.

Information send to the bot node are minimised to only needed ones.

check-frontend-ip-list can be configured according to the list, and each
element overrides previous one:

 * globally on cluster
 * default per region
 * globally per slave
 * specific per region on slave

Note: It's known that:

 {%-     set base_slave_dict = json_module.loads(slave.pop('_')) %} {#- XXX: Unsafe! #}

      is really unsafe, but for most of usage of monitoring slaves it's
      considered good enough.