test: fix pylint warnings in test_efi_bootmgr

* Use f'' strings instead of .format().
* Correct sequence of imports.
* Remove a superfluous import.
* Add missing documentation.
* Replace yield by return.

Signed-off-by: Heinrich Schuchardt <heinrich.schuchardt@canonical.com>

test/py/tests/test_efi_bootmgr/conftest.py

@@ -4,9 +4,9 @@
 """
 
 import os
-import pytest
 import shutil
-from subprocess import call, check_call
+from subprocess import check_call
+import pytest
 
 @pytest.fixture(scope='session')
 def efi_bootmgr_data(u_boot_config):
@@ -14,7 +14,7 @@ def efi_bootmgr_data(u_boot_config):
        tests
 
     Args:
-        u_boot_config: U-boot configuration.
+        u_boot_config -- U-boot configuration.
 
     Return:
         A path to disk image to be used for testing
@@ -34,9 +34,7 @@ def efi_bootmgr_data(u_boot_config):
     shutil.copyfile(u_boot_config.build_dir + '/lib/efi_loader/initrddump.efi',
                     mnt_point + '/initrddump.efi')
 
-    check_call('virt-make-fs --partition=gpt --size=+1M --type=vfat {} {}'
-               .format(mnt_point, image_path), shell=True)
-
-    print(image_path)
+    check_call(f'virt-make-fs --partition=gpt --size=+1M --type=vfat {mnt_point} {image_path}',
+               shell=True)
 
-    yield image_path
+    return image_path

test/py/tests/test_efi_bootmgr/test_efi_bootmgr.py

 # SPDX-License-Identifier:      GPL-2.0+
+""" Unit test for UEFI bootmanager
+"""
 
 import pytest
 
@@ -6,7 +8,16 @@ import pytest
 @pytest.mark.buildconfigspec('cmd_efidebug')
 @pytest.mark.buildconfigspec('cmd_bootefi_bootmgr')
 def test_efi_bootmgr(u_boot_console, efi_bootmgr_data):
-    u_boot_console.run_command(cmd = 'host bind 0 {}'.format(efi_bootmgr_data))
+    """ Unit test for UEFI bootmanager
+    The efidebug command is used to set up UEFI load options.
+    The bootefi bootmgr loads initrddump.efi as a payload.
+    The crc32 of the loaded initrd.img is checked
+
+    Args:
+        u_boot_console -- U-Boot console
+        efi_bootmgr_data -- Path to the disk image used for testing.
+    """
+    u_boot_console.run_command(cmd = f'host bind 0 {efi_bootmgr_data}')
 
     u_boot_console.run_command(cmd = 'efidebug boot add ' \
         '-b 0001 label-1 host 0:1 initrddump.efi ' \