Use same code for setting up cli/non-cli formatter

A method _create_formatter was introduced that is used for both the
log_cli_formatter and the log_formatter.

Consequences of this commit are:
* Captured logs that are output for each failing test are formatted
  using the ColoredLevelFromatter.
* caplog.text now contains ansi escape sequences.
* The formatter used for writing to a file still uses the non-colored
  logging.Formatter class.

changelog/5311.feature.rst

@@ -0,0 +1,3 @@
+Captured logs that are output for each failing test are formatted using the
+ColoredLevelFromatter.  As a consequence caplog.text contains the ANSI
+escape sequences used for coloring the level names now.

src/_pytest/logging.py

@@ -393,7 +393,7 @@ def __init__(self, config):
             config.option.verbose = 1
 
         self.print_logs = get_option_ini(config, "log_print")
-        self.formatter = logging.Formatter(
+        self.formatter = self._create_formatter(
             get_option_ini(config, "log_format"),
             get_option_ini(config, "log_date_format"),
         )
@@ -427,6 +427,19 @@ def __init__(self, config):
         if self._log_cli_enabled():
             self._setup_cli_logging()
 
+    def _create_formatter(self, log_format, log_date_format):
+        # color option doesn't exist if terminal plugin is disabled
+        color = getattr(self._config.option, "color", "no")
+        if color != "no" and ColoredLevelFormatter.LEVELNAME_FMT_REGEX.search(
+            log_format
+        ):
+            formatter = ColoredLevelFormatter(
+                create_terminal_writer(self._config), log_format, log_date_format
+            )
+        else:
+            formatter = logging.Formatter(log_format, log_date_format)
+        return formatter
+
     def _setup_cli_logging(self):
         config = self._config
         terminal_reporter = config.pluginmanager.get_plugin("terminalreporter")
@@ -437,23 +450,12 @@ def _setup_cli_logging(self):
         capture_manager = config.pluginmanager.get_plugin("capturemanager")
         # if capturemanager plugin is disabled, live logging still works.
         log_cli_handler = _LiveLoggingStreamHandler(terminal_reporter, capture_manager)
-        log_cli_format = get_option_ini(config, "log_cli_format", "log_format")
-        log_cli_date_format = get_option_ini(
-            config, "log_cli_date_format", "log_date_format"
+
+        log_cli_formatter = self._create_formatter(
+            get_option_ini(config, "log_cli_format", "log_format"),
+            get_option_ini(config, "log_cli_date_format", "log_date_format"),
         )
-        if (
-            config.option.color != "no"
-            and ColoredLevelFormatter.LEVELNAME_FMT_REGEX.search(log_cli_format)
-        ):
-            log_cli_formatter = ColoredLevelFormatter(
-                create_terminal_writer(config),
-                log_cli_format,
-                datefmt=log_cli_date_format,
-            )
-        else:
-            log_cli_formatter = logging.Formatter(
-                log_cli_format, datefmt=log_cli_date_format
-            )
+
         log_cli_level = get_actual_log_level(config, "log_cli_level", "log_level")
         self.log_cli_handler = log_cli_handler
         self.live_logs_context = lambda: catching_logs(