Comment 6 for bug 1551285

I could reproduce this issue with my preseed.
However, if I remove the part of language and keyboard selection of the preseed, and then manually selecting they as English,
this issue could not reproduce and the system would be installed successfully via PXE.

Here is what I removed:

## Locale sets language and country.
#d-i debian-installer/locale string en_US
#
## Keyboard selection.
## Disable automatic (interactive) keymap detection.
#d-i console-setup/ask_detect boolean false
#d-i keyboard-configuration/ask_detect boolean false
##d-i console-setup/modelcode string pc105
#d-i console-setup/layoutcode string us
#d-i keyboard-configuration/layoutcode string us
## To select a variant of the selected layout (if you leave this out, the
## basic form of the layout will be used):
##d-i console-setup/variantcode string dvorak