installer message about /usr/local/texlive/2019 not being writable

[Taylor, P]

Norbert Preining wrote:
> This has been the same since about 10+ years. We check the grand-parent
> folder (/usr/local) for writability.

Zdenek Wagner wrote:
> Before installing TL many years ago I created /usr/local/texlive as
> root and changed its ownership to me. Thus /usr/local is not writable
> but /usr/local/texlive is and installation works.
I cannot see how these two statements can be reconciled.  If "we" check 
the grand-parent folder (/usr/local) for writability, and Zdeněk's 
/usr/local is not writable, then theTeX Live installer should report 
that /usr/local/texlive/2019 is not writable and refused to proceed.

Norbert Preining also wrote:
> [JFBU wrote]
>> install-tl warned me about /usr/local/texlive/2019 not being writable
>> but in fact, of course, there wasn't even /usr/local/texlive to start with
> This has been the same since about 10+ years. We check the grand-parent
> folder (/usr/local) for writability.
>
> The message is correct, it is not writable and cannot be created.
If, as in JFBU's case, /usr/local/texlive/2019 does not exist, then by 
definition it is both writable and non-writable, since the empty set has 
all properties.  Thus the message is only partially correct, and is most 
certainly confusing.  "Does not exist and cannot be created" would be 
the correct diagnostic in these circumstances,

Philip Taylor