Bug#1134315: rpy2: FTBFS: E ffi.error: symbol 'R_nchar' not found in library '/usr/lib/R/lib/libR.so': /usr/lib/R/lib/libR.so: undefined symbol: R_nchar

[Rebecca N. Palmer]

Upstream also hit what was probably this bug when they moved to R 4.6.x. 
  Their response was to remove the feature that triggers it (which they 
seem to think was the only option):

https://github.com/rpy2/rpy2/pull/1241/files#diff-59f3fd61503526281cb537669c488964788676ef0e7c7f648e398d84092668a3

The 3.6.7 package currently being tested on Salsa follows upstream in 
removing the feature, but you are welcome to disagree.

(Due to unrelated issues with the R 4.5 -> 4.6 transition, this will not 
immediately get rpy2 (or statsmodels) back into testing.)