This is a workaround for what seem to be a buildout regression

Since e5687602 it's instance
responsability to generate a fonts.conf if they need fonts, but we
realized to late that if there is no /etc/fonts/fonts.conf on the
machine firefox does not start.

In recent ERP5 software release, we have a $FONTCONFIG_FILE, but on
older versions we don't.

To keep compatibility with old ERP5 software release, we generate a
default FONTCONFIG_FILE that will be used as fallback when
$FONTCONFIG_FILE environment variable is not set.

See merge request !700

This includes a workaround to fix ZSTD detection.

This allows to test the minimal setup of the configuration.

The setup is split, as slaves are now not required.

Some test methods are changed to reflect the reality of instantiation.

This reverts commit bb92b732 because of:

    CMake Error at storage/rocksdb/build_rocksdb.cmake:45 (MESSAGE):
      ZSTD library was not found, but WITH_ROCKSDBZSTD option is ON.  Either set
      WITH_ROCKSDBZSTD to OFF, or make sure ZSTD is installed

without valid fonts, firefox refuses to start

PyPDF2 overwrites `warning.showwarning` and this is already confirmed as a major flaw: https://github.com/mstamy2/PyPDF2/issues/67#issuecomment-34387142

But, this is never applied in PyPDF2.

To fix this issue in ERP5, we will copy the patch to our stack and apply it.

See merge request !746

Use by default latest version

Because we were generating a fontconfig file without the default
configuration, non optimal fonts where selected during substitutions,
for example instead of the very common Arial, we were substituting a
serif font which looks completly different.

See merge request !753

setUpModule is expensive and also the snapshot in case of error would
fail if called more than once

This is a loop invariant.