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>
diff --git a/test/py/pytest.ini b/test/py/pytest.ini
index 7e40068..e93d010 100644
--- a/test/py/pytest.ini
+++ b/test/py/pytest.ini
@@ -8,3 +8,6 @@
 markers =
     boardspec: U-Boot: Describes the set of boards a test can/can't run on.
     buildconfigspec: U-Boot: Describes Kconfig/config-header constraints.
+    notbuildconfigspec: U-Boot: Describes required disabled Kconfig options.
+    requiredtool: U-Boot: Required host tools for a test.
+    slow: U-Boot: Specific test will run slowly.