Note: the missing file 'lash.py' is supposed to be generated by swig and the version bumped from swig-2.0.11-1.fc20 to swig-3.0.0-2.fc21 in between f20 and rawhide.

CCing Jitka Plesnikova, who did the swig upgrade ...

The following 111 packages depend on 'swig' ... I believe, that the swig upgrade might be too invasive and unless majority of the packages can be rebuilt without problems using the swig 3.0.0 (current), I believe the swig should be downgraded to 2.0.12 (stable) and a new package called 'swig3' introduced in parallel ...

adonthell-0:0.3.5-1.fc21.src
amanda-0:3.3.3-11.fc21.src
apt-0:0.5.15lorg3.95-9.git522.1.fc20.src
aubio-0:0.3.2-14.fc21.src
audit-0:2.3.6-1.fc21.src
bolzplatz2006-0:1.0.3-25.fc20.src
canl-c++-0:1.0.1-1.fc21.src
cmpi-bindings-0:0.9.5-5.fc21.src
comedilib-0:0.8.1-13.fc21.src
coot-0:0.7.2-1.fc21.src
csound-0:5.19.01-1.fc20.src
cvc4-0:1.3-4.fc21.src
ecryptfs-utils-0:103-4.fc21.src
eucalyptus-0:3.3.0-0.5.20130408git32052445.fc20.src
fife-2:0.3.3r3-8.fc20.src
fityk-0:1.2.1-1.fc21.src
gdal-0:1.10.1-6.fc21.src
gdcm-0:2.4.2-1.fc21.src
gfal-0:1.16.0-3.fc21.src
ghmm-0:0.7-10.svn2286.fc20.src
gnucash-0:2.6.3-1.fc21.src
gnuradio-0:3.7.3-2.fc21.src
gr-air-modes-0:0-0.21.20140312gitcc0fa180.fc21.src
gr-osmosdr-0:0.1.1-9.20130729git9dfe3a63.fc21.src
graphviz-0:2.38.0-2.fc21.src
grass-0:6.4.3-5.fc21.src
hamlib-0:1.2.15.3-6.fc21.src
hugin-0:2013.0.0-5.fc21.src
ibutils-0:1.5.7-10.fc20.src
iguanaIR-0:1.0.5-2.fc20.src
input-pad-0:1.0.3-1.fc21.src
konkretcmpi-0:0.9.2-1.fc21.src
lash-0:0.5.4-18.fc20.src
lasso-0:2.4.0-1.fc21.src
lcg-util-0:1.16.0-2.fc21.src
lcgdm-0:1.8.8-4.fc21.src
lcms-0:1.19-11.fc21.src
ldns-0:1.6.17-2.fc21.src
lhapdf-0:5.9.1-4.fc21.src
libbatch-0:2.1.0-3.fc21.src
libcap-ng-0:0.7.3-6.fc21.src
libconcord-0:1.1-1.fc21.src
libdigidocpp-0:0.3.0-20.fc20.src
libftdi-0:0.20-5.fc20.src
libgpod-0:0.8.3-1.fc21.src
libhid-0:0.2.17-14.fc20.src
libhocr-0:0.10.17-16.fc21.src
libimobiledevice-0:1.1.5-3.fc20.src
libkdtree++-0:0.7.0-6.fc20.src
libkolabxml-0:1.0.1-2.fc21.src
libopensync-1:0.22-14.fc20.src
libpfm-0:4.4.0-5.217.gbca43a5.fc21.src
libplist-0:1.10-2.fc20.src
libselinux-0:2.2.2-6.fc21.src
libsemanage-0:2.2-3.fc21.src
libsolv-0:0.6.0-0.git05baf54.fc21.src
libteam-0:1.10-1.fc21.src
libwebp-0:0.4.0-3.fc21.src
libwfut-0:0.2.2-6.fc21.src
libyui-bindings-0:1.0.2-10.fc21.src
lilv-0:0.18.0-2.fc21.src
m2crypto-0:0.21.1-15.fc21.src
mapserver-0:6.2.1-5.fc21.src
marisa-0:0.2.4-4.fc20.src
mathgl-0:2.2.1-4.fc21.src
mypaint-0:1.1.0-1.fc20.src
nordugrid-arc-0:4.0.0-1.fc21.src
obexftp-0:0.24-1.fc21.src
openbabel-0:2.3.2-2.fc20.src
opencv-0:2.4.7-5.fc21.src
openscap-0:1.0.8-1.fc21.src
openwsman-0:2.4.4-1.fc21.src
owfs-0:2.9p1-5.fc20.src
perl-qpid-0:0.26-2.fc21.src
perl-qpid_proton-0:0.6-3.fc21.src
player-0:3.0.2-34.fc21.src
plplot-0:5.10.0-3.fc21.src
pybox2d-0:2.0.2b2-10.fc20.src
pycdio-0:0.19-3.fc21.src
pygsl-0:0.9.5-10.fc20.src
pyifp-0:0.2.2-8.fc20.src
pypop-0:0.7.0-11.fc20.src
python-libarchive-0:3.1.2.1-3.fc21.src
python-m2ext-0:0.1-4.fc20.src
python-openhpi-0:1.2-0.9.20120322svn7120.fc20.src
python-pivy-0:0.5.0-6.hg609.fc20.src
python-qpid_messaging-0:0.26-1.fc21.src
python-ufc-0:2.1.0-5.fc20.src
qpid-proton-0:0.6-2.fc21.src
qpid-qmf-0:0.24-16.fc21.src
redland-bindings-0:1.0.16.1-5.fc20.src
saga-0:2.1.1-1.fc21.src
saslwrapper-0:0.16-5.fc20.src
scipy-0:0.13.3-2.fc21.src
sdljava-0:0.9.1-24.fc21.src
setools-0:3.3.7-41.fc21.src
shogun-0:3.2.0.1-0.12.git20140317.6ee3991.fc21.src
skf-0:1.99.8-1.fc21.src
solfege-0:3.22.2-1.fc21.src
stfl-0:0.22-5.fc20.src
subversion-0:1.8.8-1.fc21.src
unbound-0:1.4.22-1.fc21.src
urjtag-0:0.10-5.fc21.20111215gite1a4227.src
vips-0:7.38.5-2.fc21.src
xrootd-1:3.3.6-1.fc21.src
zarafa-0:7.1.8-3.fc21.src
znc-0:1.2-3.fc21.src
zorba-0:3.0.0-1.fc21.src

I filtered just the packages where the latest build is f20 ... these 31 packages might fail due to the swig upgrade and need to be checked ...

apt-0:0.5.15lorg3.95-9.git522.1.fc20.src
bolzplatz2006-0:1.0.3-25.fc20.src
csound-0:5.19.01-1.fc20.src
eucalyptus-0:3.3.0-0.5.20130408git32052445.fc20.src
fife-2:0.3.3r3-8.fc20.src
ghmm-0:0.7-10.svn2286.fc20.src
ibutils-0:1.5.7-10.fc20.src
iguanaIR-0:1.0.5-2.fc20.src
lash-0:0.5.4-18.fc20.src
libdigidocpp-0:0.3.0-20.fc20.src
libftdi-0:0.20-5.fc20.src
libhid-0:0.2.17-14.fc20.src
libimobiledevice-0:1.1.5-3.fc20.src
libkdtree++-0:0.7.0-6.fc20.src
libopensync-1:0.22-14.fc20.src
libplist-0:1.10-2.fc20.src
marisa-0:0.2.4-4.fc20.src
mypaint-0:1.1.0-1.fc20.src
openbabel-0:2.3.2-2.fc20.src
owfs-0:2.9p1-5.fc20.src
pybox2d-0:2.0.2b2-10.fc20.src
pygsl-0:0.9.5-10.fc20.src
pyifp-0:0.2.2-8.fc20.src
pypop-0:0.7.0-11.fc20.src
python-m2ext-0:0.1-4.fc20.src
python-openhpi-0:1.2-0.9.20120322svn7120.fc20.src
python-pivy-0:0.5.0-6.hg609.fc20.src
python-ufc-0:2.1.0-5.fc20.src
redland-bindings-0:1.0.16.1-5.fc20.src
saslwrapper-0:0.16-5.fc20.src
stfl-0:0.22-5.fc20.src

SWIG 3.0.0 is the latest stable version. Current release doesn't mean unstable.

I admit my fault that I should rebuilt all packages which depend on swig.
I'll do it now. 

However, lash didn't failed due to swig changes. 
The problem is with version check configure* files. 
I checked the build.log and found this curious log, which helped me to find the right reason of failure.

checking for swig... /usr/bin/swig
checking for SWIG version... 3.0.0
configure: WARNING: SWIG version >= 2.0.0 is required.  You have 3.0.0.  You should look at http://www.swig.org

The configure* files are already hacked at spec to work for 2.0.0.

# Hack to build against newer swig
sed -i 's|1.3.31|2.0.0|g' configure*

I tried to update the hack to 3.0.0, and the lash was built.

I think it is easy fix.
I don't see any reason to downgraded the swig to 2.0.12 for now.
I maybe change my mind when I finish the rebuild.