Description of problem:

I have subversion repository with spec file and sources. spec file contains this line:
BuildArch:      i686

If I use mock with --scm-enable option to build directly from repository then I get this error:

DEBUG: Fetched sources from SCM
DEBUG: Preparing SCM sources
error: No compatible architectures found for build
ERROR: can't parse specfile
Traceback (most recent call last):
  File "/usr/sbin/mock", line 306, in <module>
    def do_buildsrpm(config_opts, chroot, options, args):
  File "/usr/sbin/mock", line 507, in main
    (options.sources, options.spec) = scmWorker.prepare_sources()
  File "<peak.util.decorators.rewrap wrapping mockbuild.scm.prepare_sources at 0x0277E9B0>", line 3, in prepare_sources
    def prepare_sources(self): return __decorated(self)
  File "/usr/lib/python2.7/site-packages/mockbuild/trace_decorator.py", line 70, in trace
    result = func(*args, **kw)
  File "/usr/lib/python2.7/site-packages/mockbuild/scm.py", line 136, in prepare_sources
    rpm_spec = ts.parseSpec(self.spec)
  File "/usr/lib64/python2.7/site-packages/rpm/transaction.py", line 41, in parseSpec
    return _rpmb.spec(specfile)
ValueError: can't parse specfile


It works fine if I first use mock to build src.rpm (--buildsrpm) or if I run "setarch i686 mock ..."

Version-Release number of selected component (if applicable):

mock-1.1.38-1.fc19.noarch

How reproducible:
100%

Steps to Reproduce:
1. Setup subversion repository with spec file containing "BuildArch: i686" 
2. Install mock on x86_64 host
3. mock --verbose --root fedora-19-i386 --scm-enable --scm-option <scm options>

Actual results:
mock fails

Expected results:
mock builds RPM

Additional info:

I can build other RPMs which don't specify BuildArch the same way without any problems. This only happens if spec file contains "BuildArch: i686"

The same happens with mock 1.1.39-1