debian/changelog

+htslib (1.9-4) unstable; urgency=medium
+
+  * Add Breaks: python-pysam (<< 0.15~), python3-pysam (<< 0.15~)
+    (Thanks to Graham Inggs <ginggs@debian.org>)
+    Closes: #911492
+
+ -- Andreas Tille <tille@debian.org>  Sun, 02 Dec 2018 07:54:46 +0100
+
 htslib (1.9-3) unstable; urgency=medium
 
   * debian/control: drop *i386. Closes: #905438.

debian/control

@@ -24,6 +24,7 @@ Section: libs
 Depends: ${misc:Depends},
          ${shlibs:Depends}
 Pre-Depends: ${misc:Pre-Depends}
+Breaks: python-pysam (<< 0.15~), python3-pysam (<< 0.15~)
 Description: C library for high-throughput sequencing data formats
  HTSlib is an implementation of a unified C library for accessing common file
  formats, such as SAM (Sequence Alignment/Map), CRAM and VCF (Variant Call