Revert "p-s: skip section if tarball is missing"

This reverts commit 26c59de03f43dcbf98906f1007f2482cf24b11bb.
p-s: stop section processing if the chroot-tgz is missing

and try again later

Signed-off-by: Andreas Beckmann <anbe@debian.org>
p-s: improve create_or_replace_chroot_tgz

Signed-off-by: Andreas Beckmann <anbe@debian.org>
p-s: fold create_or_replace_chroot_tgz into _check_tarball

Signed-off-by: Andreas Beckmann <anbe@debian.org>
whitespace cleanup

Signed-off-by: Andreas Beckmann <anbe@debian.org>
improve quoting of spaces

Signed-off-by: Andreas Beckmann <anbe@debian.org>
p-r: factor out a write_template_html() method

as well as Section._write_template_html()

Signed-off-by: Andreas Beckmann <anbe@debian.org>
p-r: handle general substitutions in write_template_html()

and cache the section navigation bar

Signed-off-by: Andreas Beckmann <anbe@debian.org>
p-r: insert piuparts version via Template

Signed-off-by: Andreas Beckmann <anbe@debian.org>
p-r: include md5 sum of content in the html pages

hashing skips the volatile elements md5sum, timestamp, piuparts version

Signed-off-by: Andreas Beckmann <anbe@debian.org>
p-r: fix incorrect html

and improve formatting a bit

Signed-off-by: Andreas Beckmann <anbe@debian.org>