machine: Retrieve an unique identifier if one is known.

unix-ffi/machine/machine/__init__.py

@@ -4,4 +4,13 @@
 
 
 def unique_id():
+    for base in ("/etc", "/var/lib/dbus"):
+        try:
+            with open(base + "/machine-id", "rb") as source:
+                data = source.read(32)
+                if len(data) == 32:
+                    # unhexlify might not be available
+                    return bytes([int(data[i : i + 2], 16) for i in range(0, 32, 2)])
+        except OSError as e:
+            pass
     return b"upy-non-unique"

unix-ffi/machine/manifest.py

@@ -1,4 +1,4 @@
-metadata(version="0.2.2")
+metadata(version="0.2.3")
 
 # Originally written by Paul Sokolovsky.