tests/machine_mem.py: Too non-portable, rework as an example for unix port.

examples/unix/machine_bios.py

+# This example shows how to access Video BIOS memory area via machine.mem
+# It requires root privilege and x86 legacy harfware (which has mentioned
+# Video BIOS at all).
+# It is expected to print 0xaa55, which is a signature at the start of
+# Video BIOS.
+
+import umachine as machine
+
+print(hex(machine.mem16[0xc0000]))

tests/extmod/machine_mem.py

-# This test requires root privilege, so is usually skipped
-# It also assumes x86 legacy hardware (with Video BIOS present).
-
-try:
-    import machine
-except ImportError:
-    print("SKIP")
-    import sys
-    sys.exit()
-
-try:
-    print(hex(machine.mem16[0xc0000]))
-except OSError:
-    print("SKIP")
-    import sys
-    sys.exit()

tests/extmod/machine_mem.py.exp

-0xaa55