localhost john # emerge -1va =app-shells/bash-3.2.15

These are the packages that would be merged, in order:

Calculating dependencies -
emerge: there are no ebuilds to satisfy "=app-shells/bash-3.2.15".

localhost john # emerge portage
Calculating dependencies... done!

!!! Error: the <sys-apps/portage-2.1.4_rc1 package conflicts with another package;
!!!        the two packages cannot be installed on the same system together.
!!!        Please use 'emerge --pretend' to determine blockers.

For more information about Blocked Packages, please refer to the following
section of the Gentoo Linux x86 Handbook (architecture is irrelevant):

http://www.gentoo.org/doc/en/handbook/handbook-x86.xml?full=1#blocked

localhost john # emerge --pretend portage

These are the packages that would be merged, in order:

Calculating dependencies... done!

[ebuild     U ] sys-apps/sandbox-1.2.18.1-r2 [1.2.18.1]
[ebuild     U ] dev-python/pycrypto-2.0.1-r6 [2.0.1-r5]
[ebuild     U ] sys-apps/portage-2.1.5_rc2 [2.1.3.4-r1] LINGUAS="-pl*"
*** Portage will stop merging at this point and reload itself,
    then resume the merge.
[ebuild     U ] app-shells/bash-3.2_p33 [3.2_p15-r1] USE="-plugins%"
[blocks B     ] <sys-apps/portage-2.1.4_rc1 (is blocking app-shells/bash-3.2_p33)