[Android Software/Hacking General [Developers Only]] postnobil:
Eventually gave up trying to fix the problem with installing it on my Xperia U.

Here's a log.

AROMA INSTALLER version 2.51
(c) 2012 by amarullz xda-developers

ROM Name : >>> Pimp My Rom <<<
ROM Version : 2.0
ROM Author : Androguide.fr
Device : Any android device
Start at : Mon Oct 15 15:20:23 2012

=================================
Pimp My Rom by Androguide.fr
Please be patient. I Hope you enjoyed the installer features.
=================================
Unmounting devices
about to run program [/sbin/busybox] with 3 args
umount: can't umount /system: Invalid argument
run_program: child exited with status 1
about to run program [/sbin/busybox] with 3 args
umount: can't umount /cache: Device or resource busy
run_program: child exited with status 1
>>> Setting up installation....
>>> Mounting partitions
about to run program [/sbin/busybox] with 3 args
mount: can't read '/etc/fstab': No such file or directory
run_program: child exited with status 1
about to run program [/sbin/busybox] with 3 args
mount: can't read '/etc/fstab': No such file or directory
run_program: child exited with status 1
>>> Cleaning process
about to run program [/sbin/sync] with 1 args
Backing-up original build.prop for eventual use of Un-Pimp My Rom...
about to run program [/tmp/backup_buildprop.sh] with 2 args
mkdir: can't create directory '/sdcard/PimpMyRom': File exists
cp: can't stat '/system/build.prop': No such file or directory
run_program: child exited with status 1
Original build.prop backed-up
Init.d tweaks...
Installing Touchscreen responsiveness Tweaks....
package_extract_file: can't open /system/etc/init.d/S89touch for write: No such file or directory
about to run program [/tmp/touch] with 1 args
run_program: execv failed: No such file or directory
run_program: child exited with status 1
Installing Internet Speed Tweaks....
package_extract_file: can't open /system/etc/init.d/S06netspeed for write: No such file or directory
about to run program [/tmp/netspeed] with 1 args
run_program: execv failed: No such file or directory
run_program: child exited with status 1
Installing Battery Tweaks....
package_extract_file: can't open /system/etc/init.d/S86battery for write: No such file or directory
about to run program [/tmp/battery] with 1 args
run_program: execv failed: No such file or directory
run_program: child exited with status 1
Applying Kernel Tweaks....
package_extract_file: can't open /system/etc/init.d/S07kernel for write: No such file or directory
about to run program [/tmp/kernel] with 1 args
run_program: execv failed: No such file or directory
run_program: child exited with status 1
Applying Ondemand Kernel Governor Tweaks....
package_extract_file: can't open /system/etc/init.d/S03ondemand for write: No such file or directory
about to run program [/tmp/ondemand] with 1 args
run_program: execv failed: No such file or directory
run_program: child exited with status 1
Tweaking Dalvik Virtual Machine....
package_extract_file: can't open /system/etc/init.d/S10vm for write: No such file or directory
about to run program [/tmp/vm] with 1 args
run_program: execv failed: No such file or directory
run_program: child exited with status 1
Copying sqlite3 Defragmentation bootscript....
package_extract_file: can't open /system/etc/init.d/S01defrag for write: No such file or directory
about to run program [/tmp/defrag] with 1 args
run_program: execv failed: No such file or directory
run_program: child exited with status 1
Increasing data storage by moving dalvik-cache to /cache if possible...
package_extract_file: can't open /system/etc/init.d/S41dvm2cache for write: No such file or directory
about to run program [/tmp/dvm2cache.sh] with 1 args
run_program: execv failed: No such file or directory
run_program: child exited with status 1
Bind-Mounting dalvik-cache so the device can still boot without sdcard....
package_extract_file: can't open /system/etc/init.d/S13bind for write: No such file or directory
Setting strict minimum free memory handler...
Installing ext4-fs Performance Tweak....
package_extract_file: can't open /system/etc/init.d/S84ext4 for write: No such file or directory
about to run program [/tmp/ext4] with 1 args
cat: can't open '/etc/fstab': No such file or directory
Usage: /tmp/tune2fs [-c max_mounts_count] [-e errors_behavior] [-g group]
[-i interval[d|m|w]] [-j] [-J journal_options] [-l]
[-m reserved_blocks_percent] [-o [^]mount_options[,...]]
[-r reserved_blocks_count] [-u user] [-C mount_count] [-L volume_label]
[-M last_mounted_dir] [-O [^]feature[,...]]
[-E extended-option[,...]] [-T last_check_time] [-U UUID]
[ -I new_inode_size ] device
tune2fs 1.41.12 (17-May-2010)
cat: can't open '/etc/fstab': No such file or directory
Usage: /tmp/tune2fs [-c max_mounts_count] [-e errors_behavior] [-g group]
[-i interval[d|m|w]] [-j] [-J journal_options] [-l]
[-m reserved_blocks_percent] [-o [^]mount_options[,...]]
[-r reserved_blocks_count] [-u user] [-C mount_count] [-L volume_label]
[-M last_mounted_dir] [-O [^]feature[,...]]
[-E extended-option[,...]] [-T last_check_time] [-U UUID]
[ -I new_inode_size ] device
tune2fs 1.41.12 (17-May-2010)
cat: can't open '/etc/fstab': No such file or directory
Usage: /tmp/tune2fs [-c max_mounts_count] [-e errors_behavior] [-g group]
[-i interval[d|m|w]] [-j] [-J journal_options] [-l]
[-m reserved_blocks_percent] [-o [^]mount_options[,...]]
[-r reserved_blocks_count] [-u user] [-C mount_count] [-L volume_label]
[-M last_mounted_dir] [-O [^]feature[,...]]
[-E extended-option[,...]] [-T last_check_time] [-U UUID]
[ -I new_inode_size ] device
tune2fs 1.41.12 (17-May-2010)
run_program: child exited with status 1
Enabling misc ram tweaks....
Installing Multi-Tasking Tweaks....
Installing SQLite Tweaks....
set_perm: chown of /system/xbin/sqlite3 to 0 0 failed: No such file or directory
set_perm: chmod of /system/xbin/sqlite3 to 4755 failed: No such file or directory
script aborted: set_perm: some changes failed
set_perm: some changes failed

Installer Error (Status 7)

End at : Mon Oct 15 15:20:24 2012