Module C:
import A
from B import T

logger = logging.getLogger(__name__)
# configure all loggers to sys.stdout
fileConfig("path-to-config", disable_existing_loggers=False)

def somefunc():
    # ... code that does stuff with A and logs a bunch from A's logger
    raise Exception

t = T(somefunc)
t.run()


Module A:
logger = logging.getLogger(__name__)
# ... helper functions that use logger


Module B:
stream = StringIO()
logger = logging.getLogger(__name__)

# ... code to format logger and add stream as handler

class T():
    def run(func):
        try:
            result = func(*args, **kwargs)
        except:
            send_email(stream.getvalue())

class T():
    def run(func):
        try:
            sys.stdout = stream
            result = func(*args, **kwargs)
        except:
            send_email(stream.getvalue())
        finally:
            sys.stdout = sys.__stdout__