Description of problem:
As we know, the Service Catalog depends on the namespace "kube-service-catalog" seriously. But, the namespace will not create by default in OCP 4.0.

Version-Release number of selected component (if applicable):
The catalog source is "svcat.v0.1.34" 

How reproducible:
always

Steps to Reproduce:
I list the whole steps to create the Service Catalog in below. Correct me if I'm wrong.
1. Create a namespace called "kube-service-catalog". 
Note that: you must use `adm`.
$oc adm create kube-service-catalog

2. Create an operatorgroup object. For example:
$ cat og-all.yaml 
apiVersion: operators.coreos.com/v1alpha2
kind: OperatorGroup
metadata:
  name: sc-operators
  namespace: kube-service-catalog
spec:
  selector: {}

$oc create -f og-all.yaml

3. Create a subscription of svcat. Like below:
$ cat svcat.yaml 
apiVersion: operators.coreos.com/v1alpha1
kind: Subscription
metadata:
  generateName: svcat-
  namespace: kube-service-catalog
spec:
  source: rh-operators
  name: svcat
  startingCSV: svcat.v0.1.34
  channel: alpha

$oc create -f svcat.yaml

Actual results:
The users don't aware of the namespace "kube-service-catalog" is a must.

Expected results:
We should file a doc to point this so that the users can use it smoothly.
Or do something change for the deployment of the service catalog.

Additional info: