I've upgraded my application to Python 3.7 and to the latest version of
Alembic which triggers an exception when `context.get_current_revision()`
is called.
```
File "app.py", line 395, in check_database_version
current_rev = context.get_current_revision()
File
"~/env-py3.7/lib/python3.7/site-packages/alembic/runtime/migration.py",
line 239, in get_current_revision
heads = self.get_current_heads()
File
"~/env-py3.7/lib/python3.7/site-packages/alembic/runtime/migration.py",
line 289, in get_current_heads
row[0] for row in self.connection.execute(self._version.select())
File
"~/env-py3.7/lib/python3.7/site-packages/alembic/runtime/migration.py",
line 289, in <genexpr>
row[0] for row in self.connection.execute(self._version.select())
RuntimeError: generator raised StopIteration
```
I think this is due to PEP 479.
PEP 479 <https://www.python.org/dev/peps/pep-0479> is enabled for all code
in Python 3.7, meaning that StopIteration
<https://docs.python.org/3/library/exceptions.html#StopIteration>
exceptions raised directly or indirectly in coroutines and generators are
transformed into RuntimeError
<https://docs.python.org/3/library/exceptions.html#RuntimeError>
exceptions. (Contributed by Yury Selivanov in bpo-32670
<https://bugs.python.org/issue32670>.)
I changed `ResultProxy.__iter__()` to:
```
class ResultProxy
...
def __iter__(self):
while True:
row = self.fetchone()
if row is None:
# raise StopIteration
return
else:
yield row
```
which seems to resolve the problem. Is this a problem with Alembic and an
incompatibility with Python 3.7, and is this expected to be fixed soon?
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