Finally caught this bug. It should be assigned to package initramfs-tools

https://launchpad.net/ubuntu/+source/initramfs-tools

It occurs when installing a new kernel the initramfs is regenerated and package fonts-dejavu-core is not installed. More accurately it happens when the font files cannot be found.

Some users have these particular font files removed and use those shipped with TeX Live installation. In stead of

/usr/share/fonts/truetype/dejavu/DejaVuSerifCondensed-Bold.ttf
/usr/share/fonts/truetype/dejavu/DejaVuSerif-BoldItalic.ttf
/usr/share/fonts/truetype/dejavu/DejaVuSansCondensed.ttf
/usr/share/fonts/truetype/dejavu/DejaVuSerifCondensed.ttf
/usr/share/fonts/truetype/dejavu/DejaVuSans-BoldOblique.ttf
/usr/share/fonts/truetype/dejavu/DejaVuSerifCondensed-Italic.ttf
/usr/share/fonts/truetype/dejavu/DejaVuSansCondensed-Oblique.ttf
/usr/share/fonts/truetype/dejavu/DejaVuSerif-Italic.ttf
/usr/share/fonts/truetype/dejavu/DejaVuSans-Bold.ttf
/usr/share/fonts/truetype/dejavu/DejaVuSansMono.ttf
/usr/share/fonts/truetype/dejavu/DejaVuSerifCondensed-BoldItalic.ttf
/usr/share/fonts/truetype/dejavu/DejaVuSansMono-BoldOblique.ttf
/usr/share/fonts/truetype/dejavu/DejaVuSansCondensed-Bold.ttf
/usr/share/fonts/truetype/dejavu/DejaVuSans.ttf
/usr/share/fonts/truetype/dejavu/DejaVuSansCondensed-BoldOblique.ttf
/usr/share/fonts/truetype/dejavu/DejaVuSans-ExtraLight.ttf
/usr/share/fonts/truetype/dejavu/DejaVuSerif.ttf
/usr/share/fonts/truetype/dejavu/DejaVuSerif-Bold.ttf
/usr/share/fonts/truetype/dejavu/DejaVuSansMono-Oblique.ttf
/usr/share/fonts/truetype/dejavu/DejaVuSansMono-Bold.ttf
/usr/share/fonts/truetype/dejavu/DejaVuSans-Oblique.ttf

the user has installed

/usr/local/texlive/2013/texmf-dist/fonts/truetype/public/dejavu/DejaVuSerifCondensed-Bold.ttf
/usr/local/texlive/2013/texmf-dist/fonts/truetype/public/dejavu/DejaVuSerif-BoldItalic.ttf
/usr/local/texlive/2013/texmf-dist/fonts/truetype/public/dejavu/DejaVuSansCondensed.ttf
/usr/local/texlive/2013/texmf-dist/fonts/truetype/public/dejavu/DejaVuSerifCondensed.ttf
/usr/local/texlive/2013/texmf-dist/fonts/truetype/public/dejavu/DejaVuSans-BoldOblique.ttf
/usr/local/texlive/2013/texmf-dist/fonts/truetype/public/dejavu/DejaVuSerifCondensed-Italic.ttf
/usr/local/texlive/2013/texmf-dist/fonts/truetype/public/dejavu/DejaVuSansCondensed-Oblique.ttf
/usr/local/texlive/2013/texmf-dist/fonts/truetype/public/dejavu/DejaVuSerif-Italic.ttf
/usr/local/texlive/2013/texmf-dist/fonts/truetype/public/dejavu/DejaVuSans-Bold.ttf
/usr/local/texlive/2013/texmf-dist/fonts/truetype/public/dejavu/DejaVuSansMono.ttf
/usr/local/texlive/2013/texmf-dist/fonts/truetype/public/dejavu/DejaVuSerifCondensed-BoldItalic.ttf
/usr/local/texlive/2013/texmf-dist/fonts/truetype/public/dejavu/DejaVuSansMono-BoldOblique.ttf
/usr/local/texlive/2013/texmf-dist/fonts/truetype/public/dejavu/DejaVuSansCondensed-Bold.ttf
/usr/local/texlive/2013/texmf-dist/fonts/truetype/public/dejavu/DejaVuSans.ttf
/usr/local/texlive/2013/texmf-dist/fonts/truetype/public/dejavu/DejaVuSansCondensed-BoldOblique.ttf
/usr/local/texlive/2013/texmf-dist/fonts/truetype/public/dejavu/DejaVuSans-ExtraLight.ttf
/usr/local/texlive/2013/texmf-dist/fonts/truetype/public/dejavu/DejaVuSerif.ttf
/usr/local/texlive/2013/texmf-dist/fonts/truetype/public/dejavu/DejaVuSerif-Bold.ttf
/usr/local/texlive/2013/texmf-dist/fonts/truetype/public/dejavu/DejaVuSansMono-Oblique.ttf
/usr/local/texlive/2013/texmf-dist/fonts/truetype/public/dejavu/DejaVuSansMono-Bold.ttf
/usr/local/texlive/2013/texmf-dist/fonts/truetype/public/dejavu/DejaVuSans-Oblique.ttf

In order to always find the proper files, in case they are missing from /usr/share/fonts, the initramfs generation should use fc-list to find them.

In case they are in the default place, it will return e.g.

$ fc-list DejaVuSans
/usr/share/fonts/truetype/dejavu/DejaVuSansCondensed-Oblique.ttf: DejaVu Sans,DejaVu Sans Condensed:style=Condensed Oblique,Oblique
/usr/share/fonts/truetype/dejavu/DejaVuSans-ExtraLight.ttf: DejaVu Sans,DejaVu Sans Light:style=ExtraLight
/usr/share/fonts/truetype/dejavu/DejaVuSans.ttf: DejaVu Sans:style=Book
/usr/share/fonts/truetype/dejavu/DejaVuSans-Bold.ttf: DejaVu Sans:style=Bold
/usr/share/fonts/truetype/dejavu/DejaVuSansCondensed-BoldOblique.ttf: DejaVu Sans,DejaVu Sans Condensed:style=Condensed Bold Oblique,Bold Oblique
/usr/share/fonts/truetype/dejavu/DejaVuSansCondensed.ttf: DejaVu Sans,DejaVu Sans Condensed:style=Condensed,Book
/usr/share/fonts/truetype/dejavu/DejaVuSansCondensed-Bold.ttf: DejaVu Sans,DejaVu Sans Condensed:style=Condensed Bold,Bold
/usr/share/fonts/truetype/dejavu/DejaVuSans-Oblique.ttf: DejaVu Sans:style=Oblique
/usr/share/fonts/truetype/dejavu/DejaVuSans-BoldOblique.ttf: DejaVu Sans:style=Bold Oblique

In case of a TeX Live or other installation, it will return e.g.

$ fc-list DejaVuSans
/usr/local/share/fonts/truetype/public/dejavu/DejaVuSans-Oblique.ttf: DejaVu Sans:style=Oblique
/usr/local/share/fonts/truetype/public/dejavu/DejaVuSansCondensed-Oblique.ttf: DejaVu Sans,DejaVu Sans Condensed:style=Condensed Oblique,Oblique
/usr/local/share/fonts/truetype/public/dejavu/DejaVuSansCondensed.ttf: DejaVu Sans,DejaVu Sans Condensed:style=Condensed,Book
/usr/local/share/fonts/truetype/public/dejavu/DejaVuSans-Bold.ttf: DejaVu Sans:style=Bold
/usr/local/share/fonts/truetype/public/dejavu/DejaVuSans-ExtraLight.ttf: DejaVu Sans,DejaVu Sans Light:style=ExtraLight
/usr/local/share/fonts/truetype/public/dejavu/DejaVuSans.ttf: DejaVu Sans:style=Book
/usr/local/share/fonts/truetype/public/dejavu/DejaVuSansCondensed-Bold.ttf: DejaVu Sans,DejaVu Sans Condensed:style=Condensed Bold,Bold
/usr/local/share/fonts/truetype/public/dejavu/DejaVuSansCondensed-BoldOblique.ttf: DejaVu Sans,DejaVu Sans Condensed:style=Condensed Bold Oblique,Bold Oblique
/usr/local/share/fonts/truetype/public/dejavu/DejaVuSans-BoldOblique.ttf: DejaVu Sans:style=Bold Oblique

It is important to fix this bug since it concerns communication with the user in an essential part of starting up the system. For example when the user needs to enter passphrase to decrypt a system during boot up this font is used.