qapi: Fix file name in error messages for included files

We print the name as it appears in the include expression.  Tools
processing error messages want it relative to the working directory.
Make it so.
Signed-off-by: NMarkus Armbruster <armbru@redhat.com>
Reviewed-by: NEric Blake <eblake@redhat.com>

scripts/qapi.py

@@ -101,13 +101,12 @@ class QAPIExprError(Exception):
 
 class QAPISchema:
 
-    def __init__(self, fp, fname = None, include_hist = [],
+    def __init__(self, fp, include_hist = [],
                  previously_included = [], incl_info = None):
         """ include_hist is a stack used to detect inclusion cycles
             previously_included is a global state used to avoid multiple
                                 inclusions of the same file"""
         abs_fname = os.path.abspath(fp.name)
-        if fname is None:
         fname = fp.name
         self.fname = fname
         self.include_hist = include_hist + [(fname, abs_fname)]
@@ -148,7 +147,7 @@ class QAPISchema:
                 except IOError, e:
                     raise QAPIExprError(expr_info,
                                         '%s: %s' % (e.strerror, include))
-                exprs_include = QAPISchema(fobj, include, self.include_hist,
+                exprs_include = QAPISchema(fobj, self.include_hist,
                                            previously_included, expr_info)
                 self.exprs.extend(exprs_include.exprs)
             else:

tests/qapi-schema/include-cycle.err

 In file included from tests/qapi-schema/include-cycle.json:1:
-In file included from include-cycle-b.json:1:
-include-cycle-c.json:1: Inclusion loop for include-cycle.json
+In file included from tests/qapi-schema/include-cycle-b.json:1:
+tests/qapi-schema/include-cycle-c.json:1: Inclusion loop for include-cycle.json

tests/qapi-schema/include-nested-err.err

 In file included from tests/qapi-schema/include-nested-err.json:1:
-missing-colon.json:1:10: Expected ":"
+tests/qapi-schema/missing-colon.json:1:10: Expected ":"