Comment 3 for bug 1793752

Here's last night's try:

2018-10-01 22:11:35,489 - snapcraft._store - INFO - Found cached source snap /home/cltbld/.cache/snapcraft/projects/firefox/snap_hashes/amd64/34e1c1cc8eecd87868f6409d75a156d9404154e7acb7a6120aba0b2075286459b614c6a254431c4f15e335825c38c52b.
2018-10-01 22:11:35,490 - snapcraft.internal.common - DEBUG - snapcraft is running as a snap False, SNAP_NAME set to ''
2018-10-01 22:11:35,493 - snapcraft.internal.deltas._deltas - INFO - Generating xdelta3 delta for target.snap.
2018-10-01 22:12:17,815 - snapcraft.internal.deltas._xdelta3 - DEBUG - xdelta3 delta diff generation:
VCDIFF version: 0
VCDIFF header size: 117
VCDIFF header indicator: VCD_SECONDARY VCD_APPHEADER
VCDIFF secondary compressor: lzma
VCDIFF application header: target.snap//34e1c1cc8eecd87868f6409d75a156d9404154e7acb7a6120aba0b2075286459b614c6a254431c4f15e335825c38c52b/
XDELTA filename (output): target.snap
XDELTA filename (source): 34e1c1cc8eecd87868f6409d75a156d9404154e7acb7a6120aba0b2075286459b614c6a254431c4f15e335825c38c52b
VCDIFF window number: 0
VCDIFF window indicator: VCD_SOURCE VCD_ADLER32
VCDIFF adler32 checksum: 27CB82A2
VCDIFF delta indicator: VCD_DATACOMP VCD_INSTCOMP VCD_ADDRCOMP
VCDIFF copy window length: 66894114
VCDIFF copy window offset: 0
VCDIFF delta encoding length: 6381572
VCDIFF target window length: 8388608
VCDIFF data section length: 6378979
VCDIFF inst section length: 1350
VCDIFF addr section length: 1226

2018-10-01 22:12:20,841 - snapcraft._store - INFO - Pushing delta /builds/scriptworker/work/cot/XDM1xoB8RCK0pSzqbxpUxw/public/build/target.snap.xdelta3.
Pushing target.snap.xdelta3 [============================================] 100%
Processing...|
2018-10-01 22:12:37,916 - snapcraft._store - WARNING - Error generating delta: There has been a problem while processing a snap delta.
  - Delta service failed to apply delta successfully
Falling back to pushing full snap...