#811: on Win XP let the possibility to install psutil from sources as…

… it still (kind of) works)

docs/index.rst

@@ -1924,8 +1924,12 @@ Q&A
 ===
 
 * Q: What Windows versions are supported?
-* A: From Windows Vista onwards. Latest release supporting Windows 2000, XP and
-  2003 server is psutil `3.4.2 <https://pypi.python.org/pypi?name=psutil&version=3.4.2&:action=files>`__.
+* A: From Windows **Vista** onwards. Latest binary (wheel / exe) release
+  supporting Windows **2000**, **XP** and **2003 server** which can installed
+  via pip without a compiler being installed is
+  `psutil 3.4.2 <https://pypi.python.org/pypi?name=psutil&version=3.4.2&:action=files>`__.
+  More recent psutil versions may still be compiled from sources and work
+  (more or less) but they are no longer being tested or maintained.
 
 
 Timeline

psutil/__init__.py

@@ -123,11 +123,24 @@
             pass
 
 elif WINDOWS:
-    from ._common import assert_supported_winver
-    assert_supported_winver()
-    del assert_supported_winver
+    try:
+        from . import _pswindows as _psplatform
+    except ImportError as err:
+        if sys.getwindowsversion()[0] < 6:
+            # We may get here if:
+            # 1) we are on an old Windows version
+            # 2) psutil was installed via pip + wheel
+            # See: https://github.com/giampaolo/psutil/issues/811
+            # It must be noted that psutil can still (kind of) work
+            # on outdated systems if compiled / installed from sources,
+            # but if we get here it means this this was a wheel (or exe).
+            msg = "this Windows version is too old (< Windows Vista); "
+            msg += "psutil 3.4.2 is the latest version which supports Windows "
+            msg += "2000, XP and 2003 server"
+            raise RuntimeError(msg)
+        else:
+            raise
 
-    from . import _pswindows as _psplatform
     from ._psutil_windows import ABOVE_NORMAL_PRIORITY_CLASS  # NOQA
     from ._psutil_windows import BELOW_NORMAL_PRIORITY_CLASS  # NOQA
     from ._psutil_windows import HIGH_PRIORITY_CLASS  # NOQA

psutil/_common.py

@@ -427,12 +427,3 @@ def inner(self, *args, **kwargs):
             return getattr(self, replacement)(*args, **kwargs)
         return inner
     return outer
-
-
-def assert_supported_winver():
-    """Raise an error if this Windows version is not supported."""
-    if WINDOWS and sys.getwindowsversion()[0] < 6:
-        msg = "this Windows version is too old (< Windows Vista); "
-        msg += "psutil 3.4.2 is the latest version which supports Windows "
-        msg += "2000, XP and 2003 server"
-        raise RuntimeError(msg)

setup.py

@@ -13,9 +13,10 @@
 import contextlib
 import io
 import os
+import platform
 import sys
 import tempfile
-import platform
+import warnings
 try:
     from setuptools import setup, Extension
 except ImportError:
@@ -24,7 +25,6 @@
 HERE = os.path.abspath(os.path.dirname(__file__))
 sys.path.insert(0, os.path.join(HERE, "psutil"))
 
-from _common import assert_supported_winver  # NOQA
 from _common import BSD  # NOQA
 from _common import FREEBSD  # NOQA
 from _common import LINUX  # NOQA
@@ -99,12 +99,17 @@ def write(self, s):
 
 # Windows
 if WINDOWS:
-    assert_supported_winver()
-
     def get_winver():
         maj, min = sys.getwindowsversion()[0:2]
         return '0x0%s' % ((maj * 100) + min)
 
+    if sys.getwindowsversion()[0] < 6:
+        msg = "Windows versions < Vista are no longer supported or maintained;"
+        msg = " latest supported version is psutil 3.4.2; "
+        msg += "psutil may still be installed from sources if you have "
+        msg += "Visual Studio and may also (kind of) work though"
+        warnings.warn(msg, UserWarning)
+
     macros.extend([
         # be nice to mingw, see:
         # http://www.mingw.org/wiki/Use_more_recent_defined_functions