fontconfig to make source code pro fall back to monospace, not sans-serif

gistfile1.xml

 <!-- define font family for some fonts fontconfig doesn't know about -->
 <alias>
  <family>Source Code Pro</family>
  <default><family>monospace</family></default>
 </alias>
 <alias>
  <family>Droid Sans Mono</family>
  <default><family>monospace</family></default>
 </alias>
 <alias>
  <family>PowerlineSymbols</family>
  <default><family>monospace</family></default>
 </alias>
 <!-- by default fontconfig assumes any unrecognized font is sans-serif, so -->
 <!-- the fonts above now have /both/ families.  fix this. -->
 <!-- note that "delete" applies to the first match -->
 <match>
  <test name="family" compare="eq">
   <string>sans-serif</string>
  </test>
  <test name="family" compare="eq">
   <string>monospace</string>
  </test>
  <edit name="family" mode="delete"/>
 </match>