Move importlib.abc.SourceLoader to _bootstrap.

Required updating code relying on other modules to switch to _bootstrap's
unique module requirements. This led to the realization that
get_code was being too liberal in its exception catching when calling set_data
by blindly grabbing IOError. Shifted the responsibility of safely ignoring
writes to a read-only path to set_data.

Importlib is still not relying on SourceLoader yet; requires creating a
SourcelessLoader and updating the source finder.

1 files changed, 3 insertions, 4 deletions

diff --git a/Lib/importlib/test/source/test_abc_loader.py b/Lib/importlib/test/source/test_abc_loader.py
index 62729b40e7..6bdaadb2e6 100644
--- a/Lib/importlib/test/source/test_abc_loader.py
+++ b/Lib/importlib/test/source/test_abc_loader.py
@@ -748,10 +748,9 @@ class SourceLoaderBytecodeTests(SourceLoaderTestHarness):
             return closure
 
         self.setUp(magic=b'0000')
-        for exc in (NotImplementedError, IOError):
-            self.loader.set_data = raise_exception(exc)
-            code_object = self.loader.get_code(self.name)
-            self.verify_code(code_object)
+        self.loader.set_data = raise_exception(NotImplementedError)
+        code_object = self.loader.get_code(self.name)
+        self.verify_code(code_object)
 
 class AbstractMethodImplTests(unittest.TestCase):