qapi/error: Repurpose QAPIError as an abstract base exception class

Rename QAPIError to QAPISourceError, and then create a new QAPIError
class that serves as the basis for all of our other custom exceptions,
without specifying any class properties.

This leaves QAPIError as a package-wide error class that's suitable for
any current or future errors.

(Right now, we don't have any errors that DON'T also want to specify a
Source location, but this MAY change. In these cases, a common abstract
ancestor would be desired.)

Add docstrings to explain the intended function of each error class.

Signed-off-by: John Snow <jsnow@redhat.com>
Message-Id: <20210421192233.3542904-2-jsnow@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>

1 files changed, 3 insertions, 2 deletions

diff --git a/scripts/qapi/schema.py b/scripts/qapi/schema.py
index 703b446..c277fca 100644
--- a/scripts/qapi/schema.py
+++ b/scripts/qapi/schema.py
@@ -20,7 +20,7 @@ import re
 from typing import Optional
 
 from .common import POINTER_SUFFIX, c_name
-from .error import QAPIError, QAPISemError
+from .error import QAPISemError, QAPISourceError
 from .expr import check_exprs
 from .parser import QAPISchemaParser
 
@@ -875,7 +875,8 @@ class QAPISchema:
         other_ent = self._entity_dict.get(ent.name)
         if other_ent:
             if other_ent.info:
-                where = QAPIError(other_ent.info, None, "previous definition")
+                where = QAPISourceError(other_ent.info, None,
+                                        "previous definition")
                 raise QAPISemError(
                     ent.info,
                     "'%s' is already defined\n%s" % (ent.name, where))