test/py: Manual python3 fixes

- Modern pytest is more visible in telling us about parameters that we
  had not described, so describe a few more.
- ConfigParser.readfp(...) is now configparser.read_file(...)
- As part of the "strings vs bytes" conversions in Python 3, we use the
  default encoding/decoding of utf-8 but in some places tell Python to
  replace problematic conversions rather than throw a fatal error.
- Fix a typo noticed while doing the above ("tot he" -> "to the").
- As suggested by Stephen, re-alphabetize the import list
- Per Heinrich, replace how we write contents in test_fit.py

Reviewed-by: Simon Glass <sjg@chromium.org>
Tested-by: Stephen Warren <swarren@nvidia.com>
Tested-by: Simon Glass <sjg@chromium.org> [on sandbox]
Signed-off-by: Tom Rini <trini@konsulko.com>

test/py/u_boot_spawn.py

@@ -113,7 +113,7 @@ class Spawn(object):
             Nothing.
         """
 
-        os.write(self.fd, data)
+        os.write(self.fd, data.encode(errors='replace'))
 
     def expect(self, patterns):
         """Wait for the sub-process to emit specific data.
@@ -171,7 +171,7 @@ class Spawn(object):
                 events = self.poll.poll(poll_maxwait)
                 if not events:
                     raise Timeout()
-                c = os.read(self.fd, 1024)
+                c = os.read(self.fd, 1024).decode(errors='replace')
                 if not c:
                     raise EOFError()
                 if self.logfile_read: