utils: improve logging in the get_efi_partition function

Log each partition that gets checked and make the exception messages
more informative.

src/utils/disk.py

@@ -7,6 +7,7 @@
 # (at your option) any later version.
 
 import os
+import logging
 
 import fdisk
 
@@ -45,16 +46,18 @@ def get_efi_partition(disknum):
         - /dev/{device} string
         - Partition number (starting at 1)
     """
-    try:
-        disk = get_disks()[disknum-1]
-        cxt = fdisk.Context(f'/dev/{disk}')
+    disk_index = disknum - 1
+    if disk_index < 0 or disk_index >= len(get_disks()):
+        raise ValueError(f'Invalid disk number {disknum} when trying to find ESP, {len(get_disks())} disks available.')
 
-        if cxt.label == fdisk.FDISK_DISKLABEL_DOS:
-            raise RuntimeError('Disk has DOS partition scheme, cannot find ESP.')
+    disk = get_disks()[disk_index]
+    cxt = fdisk.Context(f'/dev/{disk}')
 
-        for pa in cxt.partitions:
-            if pa.type.name == 'EFI System':
-                return cxt.partition_to_string(pa, fdisk.FDISK_FIELD_DEVICE), f'/dev/{disk}', pa.partno + 1
-    except:
-        logging.error(f'Unable to find efi partition at disk number {disknum}')
-        raise
+    if cxt.label == fdisk.FDISK_DISKLABEL_DOS:
+        raise RuntimeError(f'Disk has DOS partition scheme, cannot find ESP at /dev/{disk}')
+
+    for pa in cxt.partitions:
+        logging.info(f'Checking partition "{pa.type.name}"...')
+        if pa.type.name == 'EFI System':
+            return cxt.partition_to_string(pa, fdisk.FDISK_FIELD_DEVICE), f'/dev/{disk}', pa.partno + 1
+    raise RuntimeError(f'Cannot find "EFI System" partition at /dev/{disk}')