message: Add information to FailedLinearization for debugging
diff: @@ -45,8 +45,8 @@ pub enum ExprError {
  #[error("Cannot get index evaluation {0:?} (should have been linearized away)")]
  MissingIndexEvaluation(Column),
  - #[error("Linearization failed")]
  - FailedLinearization,
  + #[error("Linearization failed (too many unevaluated columns: {0:?}")]
  + FailedLinearization(Vec<Variable>),
  #[error("runtime table not available")]
  MissingRuntime,
  @@ -2001,7 +2001,7 @@ impl<F: Neg<Output = F> + Clone + One + Zero + PartialEq> Expr<F> {
  }
  }
  } else {
  - return Err(ExprError::FailedLinearization);
  + return Err(ExprError::FailedLinearization(unevaluated));
  }
  }
  Ok(Linearization {
  