python-stdlib/unittest/unittest: Remove f-strings.

This commit removes usage of f-strings from the unittest module, in
favour to the old printf-style raw string formatting operations.

The module is a bit special since it is meant to be also validate the
behaviour of MicroPython interpreters, and those may come with any
combination of configuration options.  For example, f-strings are not
available by default on some feature levels, and thus the test suite
won't run cleanly on certain targets unless the support for that feature
is explicitly enabled.

See the discussion at micropython/micropython#19111
for more information.

Signed-off-by: Alessandro Gatti <a.gatti@frob.it>

Author: agatti

python-stdlib/unittest/unittest/__init__.py

@@ -49,10 +49,10 @@ def __exit__(self, *exc_info):
             global __test_result__, __current_test__
             test_details = __current_test__
             if self.msg:
-                test_details += (f" [{self.msg}]",)
+                test_details += (" [%s]" % self.msg,)
             if self.params:
-                detail = ", ".join(f"{k}={v}" for k, v in self.params.items())
-                test_details += (f" ({detail})",)
+                detail = ", ".join("%s=%s" % (k, v) for k, v in self.params.items())
+                test_details += (" (%s)" % detail,)
 
             _handle_test_exception(test_details, __test_result__, exc_info, False)
         # Suppress the exception as we've captured it above
@@ -310,7 +310,7 @@ def printErrorList(self, lst):
         for c, e in lst:
             detail = " ".join((str(i) for i in c))
             print("======================================================================")
-            print(f"FAIL: {detail}")
+            print("FAIL: %s" % detail)
             print(sep)
             print(e)
 
@@ -391,7 +391,7 @@ def run_one(test_function):
         print("%s (%s) ..." % (name, suite_name), end="")
         set_up()
         __test_result__ = test_result
-        test_container = f"({suite_name})"
+        test_container = "(%s)" % suite_name
         __current_test__ = (name, test_container)
         try:
             test_result._newFailures = 0