Addon Manager: Create NetworkManager class

To enable single-login authenticated proxy use, and simplified multi-threaded
network accesses, this commit adds a new wrapper around a QNetworkAccessManager
and includes a global instantiation of the class intended to exist for the
lifetime of the program. This instance can be used to enqueue any number of
network requests, which the manager will send out to the networking subsystem
in an appropriate manner.

src/Mod/AddonManager/addonmanager_macro.py

@@ -30,9 +30,10 @@ import time
 from typing import Dict, Tuple, List, Union
 
 import FreeCAD
+from NetworkManager import AM_NETWORK_MANAGER
+
+translate = FreeCAD.Qt.translate
 
-from addonmanager_utilities import translate
-from addonmanager_utilities import urlopen
 from addonmanager_utilities import remove_directory_if_empty
 
 try:
@@ -165,28 +166,25 @@ class Macro(object):
 
     def fill_details_from_wiki(self, url):
         code = ""
-        u = urlopen(url)
-        if u is None:
+        p = AM_NETWORK_MANAGER.blocking_get(url)
+        if not p:
             FreeCAD.Console.PrintWarning(
                 translate(
                     "AddonsInstaller",
-                    f"Could not connect to {url} - check connection and proxy settings",
+                    f"Unable to open macro wiki page at {url}",
                 )
                 + "\n"
             )
             return
-        p = u.read()
-        if isinstance(p, bytes):
-            p = p.decode("utf-8")
-        u.close()
+        p = p.data().decode("utf8")
         # check if the macro page has its code hosted elsewhere, download if
         # needed
         if "rawcodeurl" in p:
             rawcodeurl = re.findall('rawcodeurl.*?href="(http.*?)">', p)
             if rawcodeurl:
                 rawcodeurl = rawcodeurl[0]
-                u2 = urlopen(rawcodeurl)
-                if u2 is None:
+                u2 = AM_NETWORK_MANAGER.blocking_get(rawcodeurl)
+                if not u2:
                     FreeCAD.Console.PrintWarning(
                         translate(
                             "AddonsInstaller",
@@ -195,18 +193,7 @@ class Macro(object):
                         + "\n"
                     )
                     return
-                response = ""
-                block = 8192
-                while True:
-                    data = u2.read(block)
-                    if not data:
-                        break
-                    if isinstance(data, bytes):
-                        data = data.decode("utf-8")
-                    response += data
-                if response:
-                    code = response
-                u2.close()
+                code = u2.data().decode("utf8")
         if not code:
             code = re.findall(r"<pre>(.*?)</pre>", p.replace("\n", "--endl--"))
             if code: