Raise error on pip install dbt (#4133)

* Raise error on pip install dbt

* Fix relative path logic

* Do not build dist for dbt

* Fix long descriptions

* Trigger code checks

* Using root readme more trouble than good

* only fail on install, not build

* Edit dist script. Avoid README duplication

* jk, be less clever

* Ignore 'dbt' source distribution when testing

* Add changelog entry

Co-authored-by: Kyle Wigley <kyle@dbtlabs.com>

automatic commit by git-black, original commits:
  dd84f9a

core/setup.py

@@ -20,7 +20,7 @@
 
 
 this_directory = os.path.abspath(os.path.dirname(__file__))
-with open(os.path.join(this_directory, 'README.md')) as f:
+with open(os.path.join(this_directory, "README.md")) as f:
     long_description = f.read()
 
 
@@ -35,7 +35,7 @@
     version=package_version,
     description=description,
     long_description=long_description,
-    long_description_content_type='text/markdown',
+    long_description_content_type="text/markdown",
     author="dbt Labs",
     author_email="info@dbtlabs.com",
     url="https://github.com/dbt-labs/dbt-core",