Description of problem:

When no DNS resolver is configured, such as in the RPM mock build environment, the “eventlet” package does not even import successfully.

Version-Release number of selected component (if applicable): 0.32.0-2.fc36


How reproducible:


Steps to Reproduce:
1. $ mock -r fedora-rawhide-x86_64 --clean
2. $ mock -r fedora-rawhide-x86_64 -i python3-eventlet
3. $ mock -r fedora-rawhide-x86_64 --shell
4. <mock-chroot> sh-5.1# python3 -c 'import eventlet'

Actual results:

Traceback (most recent call last):
  File "<string>", line 1, in <module>
  File "/usr/lib/python3.10/site-packages/eventlet/__init__.py", line 17, in <module>
    from eventlet import convenience
  File "/usr/lib/python3.10/site-packages/eventlet/convenience.py", line 7, in <module>
    from eventlet.green import socket
  File "/usr/lib/python3.10/site-packages/eventlet/green/socket.py", line 21, in <module>
    from eventlet.support import greendns
  File "/usr/lib/python3.10/site-packages/eventlet/support/greendns.py", line 411, in <module>
    resolver = ResolverProxy(hosts_resolver=HostsResolver())
  File "/usr/lib/python3.10/site-packages/eventlet/support/greendns.py", line 325, in __init__
    self.clear()
  File "/usr/lib/python3.10/site-packages/eventlet/support/greendns.py", line 328, in clear
    self._resolver = dns.resolver.Resolver(filename=self._filename)
  File "/usr/lib/python3.10/site-packages/dns/resolver.py", line 734, in __init__
    self.read_resolv_conf(filename)
  File "/usr/lib/python3.10/site-packages/dns/resolver.py", line 826, in read_resolv_conf
    raise NoResolverConfiguration
dns.resolver.NoResolverConfiguration: Resolver configuration could not be read or specified no nameservers.


Expected results:

(no output)

Additional info:

This works fine in python-eventlet-0.31.1-1.fc35 and earlier. The change breaks any Fedora package that uses eventlet in its tests. One example is python-engineio.