debuginstall: gracefully handle missing __file__ attributes

debuginstall: gracefully handle missing __file__ attributes

This was crashing PyOxidizer.  While here, point "Python lib" and "installed
modules" to the oxidized binary when read from memory instead of pretending
their location is unknown.

Differential Revision: https://phab.mercurial-scm.org/D7451

--- a/mercurial/debugcommands.py	Sat Nov 16 16:25:28 2019 +0900
+++ b/mercurial/debugcommands.py	Sun Nov 17 01:00:06 2019 -0500
@@ -1470,6 +1470,12 @@
     )
 
     # Python
+    pythonlib = None
+    if util.safehasattr(os, '__file__'):
+        pythonlib = os.path.dirname(pycompat.fsencode(os.__file__))
+    elif getattr(sys, 'oxidized', False):
+        pythonlib = pycompat.sysexecutable
+
     fm.write(
         b'pythonexe',
         _(b"checking Python executable (%s)\n"),
@@ -1483,7 +1489,7 @@
     fm.write(
         b'pythonlib',
         _(b"checking Python lib (%s)...\n"),
-        os.path.dirname(pycompat.fsencode(os.__file__)),
+        pythonlib or _(b"unknown"),
     )
 
     security = set(sslutil.supportedprotocols)
@@ -1527,13 +1533,19 @@
     )
 
     # compiled modules
+    hgmodules = None
+    if util.safehasattr(sys.modules[__name__], '__file__'):
+        hgmodules = os.path.dirname(pycompat.fsencode(__file__))
+    elif getattr(sys, 'oxidized', False):
+        hgmodules = pycompat.sysexecutable
+
     fm.write(
         b'hgmodulepolicy', _(b"checking module policy (%s)\n"), policy.policy
     )
     fm.write(
         b'hgmodules',
         _(b"checking installed modules (%s)...\n"),
-        os.path.dirname(pycompat.fsencode(__file__)),
+        hgmodules or _(b"unknown"),
     )
 
     rustandc = policy.policy in (b'rust+c', b'rust+c-allow')