add optional role argument, fix messaging around permissions errors

Makefile

@@ -3,7 +3,7 @@
 changed_tests := `git status --porcelain | grep '^\(M\| M\|A\| A\)' | awk '{ print $$2 }' | grep '\/test_[a-zA-Z_\-\.]\+.py'`
 
 install:
-	pip install .
+	pip install --upgrade .
 
 test:
 	@echo "Full test run starting..."

dbt/adapters/snowflake.py

@@ -30,6 +30,13 @@ def exception_handler(connection, cursor, model_name, query):
     except snowflake.connector.errors.ProgrammingError as e:
         if 'Empty SQL statement' in e.msg:
             logger.debug("got empty sql statement, moving on")
+        elif 'This session does not have a current database' in e.msg:
+            handle.rollback()
+            raise dbt.exceptions.FailedToConnectException(
+                ('{}\n\nThis error sometimes occurs when invalid credentials '
+                 'are provided, or when your default role does not have '
+                 'access to use the specified database. Please double check '
+                 'your profile and try again.').format(str(e)))
         else:
             handle.rollback()
             raise dbt.exceptions.ProgrammingException(str(e))
@@ -96,6 +103,7 @@ def open_connection(cls, connection):
                 database=credentials.get('database'),
                 schema=credentials.get('schema'),
                 warehouse=credentials.get('warehouse'),
+                role=credentials.get('role', None),
                 autocommit=False
             )
 

dbt/contracts/connection.py

@@ -1,4 +1,4 @@
-from voluptuous import Schema, Required, All, Any, Extra, Range
+from voluptuous import Schema, Required, All, Any, Extra, Range, Optional
 from voluptuous.error import MultipleInvalid
 
 from dbt.exceptions import ValidationException
@@ -28,6 +28,7 @@
     Required('database'): str,
     Required('schema'): str,
     Required('warehouse'): str,
+    Optional('role'): str,
 })
 
 credentials_mapping = {

dbt/main.py

@@ -104,7 +104,8 @@ def run_from_args(parsed):
         dbt.tracking.track_invocation_end(
             project=proj, args=parsed, result_type="ok", result=None
         )
-    except dbt.exceptions.NotImplementedException as e:
+    except (dbt.exceptions.NotImplementedException,
+            dbt.exceptions.FailedToConnectException) as e:
         logger.info('ERROR: {}'.format(e))
         dbt.tracking.track_invocation_end(
             project=proj, args=parsed, result_type="error", result=str(e)