If you're assuming a known-good Python stack, then a pure-python solution will just work. Using Solr/Lucene means having a known-good Python stack and a known-good JVM. Python is installed with most (all?) Linux distributions by default, but Java is almost never part of the base install.

Also, a pure-python solution allows for an in-process index/search, rather than adding another external process dependency which needs to be monitored and maintained.