We can apply patches like this, but I'm not sure that unconditionally logging in when initializing APISite is a good idea.

diff --git a/pywikibot/comms/eventstreams.py b/pywikibot/comms/eventstreams.py
index cd9c280c3..aacc4be54 100644
--- a/pywikibot/comms/eventstreams.py
+++ b/pywikibot/comms/eventstreams.py
@@ -143,7 +143,10 @@ class EventStreams(GeneratorWrapper):
                               'install it with "pip install sseclient"\n')
         self.filter = {'all': [], 'any': [], 'none': []}
         self._total = None
-        self._site = kwargs.pop('site', Site())
+        if 'site' in kwargs:
+            self._site = kwargs.pop('site')
+        else:
+            self._site = Site()

The problem is that the pop default is evaluated even if it is not needed:

x = {'foo': 'bar'}
def baz(): print('quez')

x.pop('foo', baz())
quez
'bar'

Here some other samples:
https://codesearch.wmcloud.org/pywikibot/?q=%28get%7Cpop%29%5C%28%5B%5E+%2C%5C%29%5D%2B%2C+%5B%5E%5C%28%5C%29%5D%2B%5C%28&files=&excludeFiles=&repos=

dict should have been implemented like that instead:

class lazy_dict(dict):
    sentinel = object()
    def pop(value, default=sentinel):
        try:
            r = super.pop(value)
        except KeyError:
            if default is sentinel:
                raise
            r = default
        return r

but it is a C function

Change 915392 had a related patch set uploaded (by Xqt; author: Xqt):

[pywikibot/core@master] [IMPR] do not evaluate Site() with dict.pop() as default value

https://gerrit.wikimedia.org/r/915392

In T335720#8825687, @Xqt wrote:

The problem is that the pop default is evaluated even if it is not needed:

x = {'foo': 'bar'}
def baz(): print('quez')

x.pop('foo', baz())
quez
'bar'

Here some other samples:
https://codesearch.wmcloud.org/pywikibot/?q=%28get%7Cpop%29%5C%28%5B%5E+%2C%5C%29%5D%2B%2C+%5B%5E%5C%28%5C%29%5D%2B%5C%28&files=&excludeFiles=&repos=

dict should have been implemented like that instead:

class lazy_dict(dict):
    sentinel = object()
    def pop(value, default=sentinel):
        try:
            r = super.pop(value)
        except KeyError:
            if default is sentinel:
                raise
            r = default
        return r

but it is a C function

See https://bugs.python.org/issue39083

Change 915392 merged by jenkins-bot:

[pywikibot/core@master] [IMPR] do not evaluate Site() with dict.pop() as default value

https://gerrit.wikimedia.org/r/915392