Simplify `command.easy_install.get_site_dirs`

setuptools/command/easy_install.py

@@ -1371,7 +1371,9 @@ def get_site_dirs():
     if sys.exec_prefix != sys.prefix:
         prefixes.append(sys.exec_prefix)
     for prefix in prefixes:
-        if prefix:
+        if not prefix:
+            continue
+
         if sys.platform in ('os2emx', 'riscos'):
             sitedirs.append(os.path.join(prefix, "Lib", "site-packages"))
         elif os.sep == '/':
@@ -1389,13 +1391,19 @@ def get_site_dirs():
                 prefix,
                 os.path.join(prefix, "lib", "site-packages"),
             ])
-            if sys.platform == 'darwin':
+        if sys.platform != 'darwin':
+            continue
+
         # for framework builds *only* we add the standard Apple
         # locations. Currently only per-user, but /Library and
         # /Network/Library could be added too
-                if 'Python.framework' in prefix:
+        if 'Python.framework' not in prefix:
+            continue
+
         home = os.environ.get('HOME')
-                    if home:
+        if not home:
+            continue
+
         home_sp = os.path.join(
             home,
             'Library',
@@ -1405,17 +1413,14 @@ def get_site_dirs():
         )
         sitedirs.append(home_sp)
     lib_paths = get_path('purelib'), get_path('platlib')
-    for site_lib in lib_paths:
-        if site_lib not in sitedirs:
-            sitedirs.append(site_lib)
+
+    sitedirs.extend(s for s in lib_paths if s not in sitedirs)
 
     if site.ENABLE_USER_SITE:
         sitedirs.append(site.USER_SITE)
 
-    try:
+    with contextlib.suppress(AttributeError):
         sitedirs.extend(site.getsitepackages())
-    except AttributeError:
-        pass
 
     sitedirs = list(map(normalize_path, sitedirs))