A simple yet workable solution is to enclose the \bibliography command somewhere it is never executed. Here are various methods:
\iffalse
\bibliography{test1.bib}
\bibliography{test2.bib}
\fi
\newcommand\NEVERRUNME{
\bibliography{test1.bib}
\bibliography{test2.bib}
}
They provide what Kile reads but never parses it...
It does not do what Kile is supposed to do, however, you cheat Kile in to thinking the correct thing.
Your error message indicates that you are using biblatex, which supports many different backends: bibtex, bibtex8, bibtexu, biber. It now defaults to biber, since it was designed specifically for biblatex and provides much more functionality than any bibtex-based backends. If you want to use a different backend, say bibtex, you need to inform biblatex by adding the appropriate option (among any others you also wish to use):
\usepackage[backend=bibtex]{biblatex}
There are also implications for what files need to be processed based on the backend. With bibtex, you use the .aux file to create the bibliography; the command sequence is:
latex myfile.tex
bibtex myfile.aux
latex myfile.tex
latex myfile.tex
(Note that the file extension does not need to be said explicitly, but these are the specific files that latex and bibtex are using.)
With biber it is slightly different:
latex myfile.tex
biber myfile.bcf
latex myfile.tex
(Note again that the extensions are unnecessary. Also, other packages might need a third latex run, but biber doesn't unless you do something like writing a \cite command in an entry in your .bib file. It also doesn't hurt to remind yourself that you are using biber by specifying backend=biber in your loading of biblatex.)
Now, in order to get Kile to know you are using biber instead of bibtex, you probably need to change some of the default settings. I don't use Kile and no longer have it installed, but according to the documentation, you can access these settings in 'Settings -> Configure Kile... -> Tools+Build in the General tab in the LaTeX and PDFLaTeX tools`
Best Answer
I encountered the same problem that Kile (2.9.93 on LinuxMint 19) did not autocomplete bibtex entries.
In my case, this was caused by a somewhat unusual organization of project files: I have the bib file in a central place and placed a symbolic link into my project directory. For BiTeX that was fine, but Kile (2.9.93) did not autocomplete bibtex entries.
The solution for that (unusual) case was to replace the symbolic link with a hard link.