[tl2021/texdoc] texdoc reporting spurious error on Windows

[Ilya Zakharevich]

Doing (on Windows with stock TexLive2021) 
    texdoc -D texdoc
gives a lot of messages irrelevant to this discussion (but which include
    
   texdoc debug-config: Setting "viewer_pdf=sumatraPDF" from environment variable "PDFVIEWER_texdoc".
   texdoc debug-config: Ignoring "viewer_pdf=sumatraPDF" from environment variable "PDFVIEWER".

), then does

  texdoc debug-view: Using "viewer_pdf" to open the file.
  texdoc info: View command: sumatraPDF "d:\programs\texlive\2021.local\texmf-dist\doc\support\texdoc\texdoc.pdf"
  texdoc info: Setting environment LC_CTYPE to: English_United States.1252
  texdoc error: Failed to execute: sumatraPDF "d:\programs\texlive\2021.local\texmf-dist\doc\support\texdoc\texdoc.pdf"

The documentation is open successfully (by sumatraPDF!), but the last
error line is produced even without “-D” flag.

  (I have
      PDFVIEWER=sumatraPDF
      PDFVIEWER_texdoc=sumatraPDF
   in environment.)

Hope this helps,
Ilya