Code
T0015 cannot-read
files.text was asked for the words of a file of a kind that no reader knows, or of a file that its reader cannot read.
Details
The engine reads plain text, Markdown, CSV, JSON and any other text/*, HTML, a Word document (.docx) and a PDF. The kind is the one stored with the file, and the ending of its name decides where the kind says nothing. A file that states the kind of a Word document and is none fails with this code too.
The fix
Read a file of a kind that a reader knows, or connect a TextReader for the kind in engine.ts. Where the kind that is stored with the file is wrong, code with full access sets it with files.setKind.