Update releasenotes and apply review feedback

Author: michaelosthege

RELEASE-NOTES.md

@@ -1,11 +1,20 @@
 # Release Notes
 
-## PyMC3 3.10.1 (on deck)
+## PyMC3 3.11.0 (on deck)
+This release breaks some APIs w.r.t. `3.10.0`.
+It also brings some dreadfully awaited fixes, so be sure to go through the changes below.
+(Or latest when you run into problems.)
 
 ### Maintenance
+- Changed shape behavior: __No longer collapse length 1 vector shape into scalars.__ (see [#4206](https://github.com/pymc-devs/pymc3/issue/4206) and [#4214](https://github.com/pymc-devs/pymc3/pull/4214))
+  - __Applies to random variables and also the `.random(size=...)` kwarg!__
+  - To create scalar variables you must now use `shape=None` or `shape=()`.
+  - __`shape=(1,)` and `shape=1` now become vectors.__ Previously they were collapsed into scalars
+  - 0-length dimensions are now ruled illegal for random variables and raise a `ValueError`.
 - Fixed bug whereby partial traces returns after keyboard interrupt during parallel sampling had fewer draws than would've been available [#4318](https://github.com/pymc-devs/pymc3/pull/4318)
 - Make `sample_shape` same across all contexts in `draw_values` (see [#4305](https://github.com/pymc-devs/pymc3/pull/4305)).
 - Removed `theanof.set_theano_config` because it illegally touched Theano's privates (see [#4329](https://github.com/pymc-devs/pymc3/pull/4329)).
+- In `sample_prior_predictive` the `vars` kwarg was removed in favor of `var_names` (see [#4327](https://github.com/pymc-devs/pymc3/pull/4327))
 
 
 ## PyMC3 3.10.0 (7 December 2020)

pymc3/distributions/distribution.py

@@ -1007,14 +1007,6 @@ def _draw_value(param, point=None, givens=None, size=None):
     raise ValueError("Unexpected type in draw_value: %s" % type(param))
 
 
-def _is_one_d(dist_shape):
-    if hasattr(dist_shape, "dshape") and dist_shape.dshape in {()}:
-        return True
-    elif hasattr(dist_shape, "shape") and dist_shape.shape in {()}:
-        return True
-    return False
-
-
 def generate_samples(generator, *args, **kwargs):
     """Generate samples from the distribution of a random variable.
 
@@ -1048,8 +1040,6 @@ def generate_samples(generator, *args, **kwargs):
     Any remaining args and kwargs are passed on to the generator function.
     """
     dist_shape = kwargs.pop("dist_shape", ())
-    # TODO: the following variable is no longer used !!
-    one_d = _is_one_d(dist_shape)
     size = kwargs.pop("size", None)
     broadcast_shape = kwargs.pop("broadcast_shape", None)
     not_broadcast_kwargs = kwargs.pop("not_broadcast_kwargs", None)