ppa-purge fails to remove packages when ppa repository includes a plus in the name

When ppa-purge attempts to disable a repository that has a plus in the name, it fails because sed interprets the plus as part of the regular expression.

When running sudo ppa-purge ppa:avsm/ocaml42+opam120, here is the argument passed to sed:

\:^[^#]+/avsm/ocaml42+opam120/:s/^deb/# deb/

Note that this should be:

\:^[^#]+/avsm/ocaml42\+opam120/:s/^deb/# deb/

Here is the output I get, showing that the package versions don't change because the repository is not actually removed:

fuzz@UbuFuzz:/etc/apt/sources.list.d$ sudo ppa-purge ppa:avsm/ocaml42+opam120
Updating packages lists
PPA to be removed: avsm ocaml42+opam120
Package revert list generated:
 camlp4/trusty camlp4-extra/trusty ocaml/trusty ocaml-base/trusty
ocaml-base-nox/trusty ocaml-compiler-libs/trusty ocaml-interp/trusty
ocaml-mode/trusty ocaml-native-compilers/trusty ocaml-nox/trusty opam/trusty
opam-docs/trusty

Disabling avsm PPA from /etc/apt/sources.list.d/avsm-ocaml42_opam120-trusty.list
\:^[^#]+/avsm/ocaml42+opam120/:s/^deb/# deb/
Updating packages lists
Reading package lists... Done
Building dependency tree
Reading state information... Done
camlp4 is already the newest version.
ocaml is already the newest version.
ocaml-base is already the newest version.
ocaml-base-nox is already the newest version.
ocaml-compiler-libs is already the newest version.
ocaml-interp is already the newest version.
ocaml-native-compilers is already the newest version.
ocaml-nox is already the newest version.
ocaml-mode is already the newest version.
camlp4-extra is already the newest version.
opam is already the newest version.
opam-docs is already the newest version.
Selected version '4.02.1+3-1ppa1~trusty' (OCaml 4.02.1 + OPAM 1.2.0:14.04/trusty [i386]) for 'camlp4'
Selected version '4.02.1+3-1ppa1~trusty' (OCaml 4.02.1 + OPAM 1.2.0:14.04/trusty [i386]) for 'camlp4-extra'
Selected version '4.02.1-1ppa3~trusty' (OCaml 4.02.1 + OPAM 1.2.0:14.04/trusty [i386]) for 'ocaml'
Selected version '4.02.1-1ppa3~trusty' (OCaml 4.02.1 + OPAM 1.2.0:14.04/trusty [i386]) for 'ocaml-base'
Selected version '4.02.1-1ppa3~trusty' (OCaml 4.02.1 + OPAM 1.2.0:14.04/trusty [i386]) for 'ocaml-base-nox'
Selected version '4.02.1-1ppa3~trusty' (OCaml 4.02.1 + OPAM 1.2.0:14.04/trusty [i386]) for 'ocaml-compiler-libs'
Selected version '4.02.1-1ppa3~trusty' (OCaml 4.02.1 + OPAM 1.2.0:14.04/trusty [i386]) for 'ocaml-interp'
Selected version '4.02.1-1ppa3~trusty' (OCaml 4.02.1 + OPAM 1.2.0:14.04/trusty [all]) for 'ocaml-mode'
Selected version '4.02.1-1ppa3~trusty' (OCaml 4.02.1 + OPAM 1.2.0:14.04/trusty [i386]) for 'ocaml-native-compilers'
Selected version '4.02.1-1ppa3~trusty' (OCaml 4.02.1 + OPAM 1.2.0:14.04/trusty [i386]) for 'ocaml-nox'
Selected version '1.2.0-1ppa1~trusty' (OCaml 4.02.1 + OPAM 1.2.0:14.04/trusty [i386]) for 'opam'
Selected version '1.2.0-1ppa1~trusty' (OCaml 4.02.1 + OPAM 1.2.0:14.04/trusty [all]) for 'opam-docs'
0 upgraded, 0 newly installed, 0 to remove and 35 not upgraded.
PPA purged successfully

fuzz@UbuFuzz:/etc/apt/sources.list.d$ cat /etc/apt/sources.list.d/avsm-ocaml42_opam120-trusty.list
deb http://ppa.launchpad.net/avsm/ocaml42+opam120/ubuntu trusty main
deb-src http://ppa.launchpad.net/avsm/ocaml42+opam120/ubuntu trusty main