Bug#1027215: Proposed RM: theano, keras, deepnano -- broken by numpy 1.24, theano mostly abandoned upstream

Control: reopen -1 1026539

theano has been mostly abandoned upstream since 2018.  (The Aesara fork 
is not abandoned, but includes interface changes including the import 
name, so would break reverse dependencies not specifically altered for it.)

It is currently broken (FTBFS due to multiple test failures), probably 
by numpy 1.24 (#1027215).

Its reverse dependencies (keras and deepnano) are both also broken by 
this.  (keras _also_ has apparently unrelated problems, #1026738, and is 
orphaned, #1027938.)

This was previously discussed in #1027215, where it was noted that 
removing keras would also block the addition of qmean (ITP #976981), but 
attempts to fix it failed.  (Note that what is in Salsa isn't actually a 
fix: theano skips most of its tests in Salsa CI because they take 
several hours.)