[internal] use xml-rpc api to get owners (pantsbuild#11901)

Calling an API is better than scraping a web site, and the results are the same.
This also allows the removal of bs4 dependency in pants.

https://warehouse.pypa.io/api-reference/xml-rpc.html?highlight=maintainer#package-querying


<img width="670" alt="Screen Shot 2021-04-12 at 9 28 24 PM" src="https://user-images.githubusercontent.com/1268088/114497470-13f48d00-9bd7-11eb-9580-d3776c2215f7.png">
<img width="1284" alt="Screen Shot 2021-04-12 at 9 29 23 PM" src="https://user-images.githubusercontent.com/1268088/114497472-1525ba00-9bd7-11eb-88ff-4f4bdce6518c.png">

3rdparty/python/BUILD

@@ -5,7 +5,6 @@
 python_requirements(
   module_mapping={
     "ansicolors": ["colors"],
-    "beautifulsoup4": ["bs4"],
     "PyYAML": ["yaml"],
     "setuptools": ["pkg_resources"],
   }

3rdparty/python/constraints.txt

@@ -1,7 +1,6 @@
-# Generated by build-support/bin/generate_lockfile.sh on Mon Apr 12 19:49:47 MST 2021
+# Generated by build-support/bin/generate_lockfile.sh on Tue Apr 13 10:17:21 PDT 2021
 ansicolors==1.1.8
 attrs==20.3.0
-beautifulsoup4==4.9.3
 bugout==0.1.11
 certifi==2020.12.5
 cffi==1.14.5
@@ -32,7 +31,6 @@ requests==2.25.1
 setproctitle==1.2.2
 setuptools==53.1.0
 six==1.15.0
-soupsieve==2.2.1
 toml==0.10.2
 typed-ast==1.4.3
 typing-extensions==3.7.4.3

3rdparty/python/requirements.txt

@@ -1,5 +1,4 @@
 ansicolors==1.1.8
-beautifulsoup4>=4.9,<4.10
 fasteners==0.16
 freezegun==1.1.0
 

build-support/bin/packages.py

@@ -9,6 +9,7 @@
 import shutil
 import subprocess
 import sys
+import xmlrpc.client
 from configparser import ConfigParser
 from contextlib import contextmanager
 from functools import total_ordering
@@ -19,7 +20,6 @@
 from xml.etree import ElementTree
 
 import requests
-from bs4 import BeautifulSoup
 from common import banner, die, green, travis_section
 from reversion import reversion
 
@@ -69,15 +69,9 @@ def latest_published_version(self) -> str:
         return cast(str, json_data["info"]["version"])
 
     def owners(self) -> set[str]:
-        url_content = requests.get(
-            f"https://pypi.org/project/{self.name}/{self.latest_published_version()}/"
-        ).text
-        parser = BeautifulSoup(url_content, "html.parser")
-        owners = {
-            span.find("a", recursive=False).get_text().strip().lower()
-            for span in parser.find_all("span", class_="sidebar-section__maintainer")
-        }
-        return owners
+        client = xmlrpc.client.ServerProxy("https://pypi.org/pypi")
+        roles = client.package_roles(self.name)
+        return {row[1] for row in roles if row[0] == "Owner"}  # type: ignore[union-attr,index]
 
 
 PACKAGES = sorted(