Add some Py3-only builtin names (mostly I/O exceptions) as uncachable builtins...

Add some Py3-only builtin names (mostly I/O exceptions) as uncachable builtins to avoid "unknown name" errors when running Cython in Py2.
Closes #2087.

CHANGES.rst

@@ -102,6 +102,9 @@ Bugs fixed
   the type of the first argument as ``self``.  It was previously treated as plain
   object, but CPython actually guarantees that it always has the correct type.
 
+* Some Python 3 exceptions were not recognised as builtins when running Cython
+  under Python 2.
+
 * Some async helper functions were not defined in the generated C code when
   compiling simple async code.  (Github issue #2075)
 

Cython/Compiler/Code.py

@@ -60,10 +60,42 @@ basicsize_builtins_map = {
 }
 
 uncachable_builtins = [
-    # builtin names that cannot be cached because they may or may not
-    # be available at import time
+    # Global/builtin names that cannot be cached because they may or may not
+    # be available at import time, for various reasons:
+    ## - Py3.7+
+    'breakpoint',  # might deserve an implementation in Cython
+    ## - Py3.4+
+    '__loader__',
+    '__spec__',
+    ## - Py3+
+    'BlockingIOError',
+    'BrokenPipeError',
+    'ChildProcessError',
+    'ConnectionAbortedError',
+    'ConnectionError',
+    'ConnectionRefusedError',
+    'ConnectionResetError',
+    'FileExistsError',
+    'FileNotFoundError',
+    'InterruptedError',
+    'IsADirectoryError',
+    'ModuleNotFoundError',
+    'NotADirectoryError',
+    'PermissionError',
+    'ProcessLookupError',
+    'RecursionError',
+    'ResourceWarning',
+    #'StopAsyncIteration',  # backported
+    'TimeoutError',
+    '__build_class__',
+    'ascii',  # might deserve an implementation in Cython
+    #'exec',  # implemented in Cython
+    ## - Py2.7+
+    'memoryview',
+    ## - platform specific
     'WindowsError',
-    '_',  # e.g. gettext
+    ## - others
+    '_',  # e.g. used by gettext
 ]
 
 special_py_methods = set([