travis: Add /usr/local/lib/python3/dist-packages/ to PYTHONPATH

and run ldconfig after installing gr-iqbal and gr-osmosdr.

Due to debian-python-install patch [1] the OOT packages are installed in
/usr/local/lib/python3/dist-packages but this path is not in the python3
default search paths (sys.path) and because of this importing OOT
modules fails.

[1] https://salsa.debian.org/bottoms/pkg-gnuradio/blob/25e1de07/debian/patches/debian-python-install

Change-Id: I260c82d1a53dab85f7aac86f23e61309d8841255

Author: velichkov

tests/dockerfiles/Debian_testing.docker

@@ -26,19 +26,21 @@ RUN git clone --branch maint-3.8 --recurse-submodules https://github.com/velichk
     mkdir build && \
     cd build && \
     cmake .. && \
-    make -j $(nproc) install
+    make -j $(nproc) install && \
+    ldconfig
 
 RUN git clone --branch maint-3.8 https://github.com/velichkov/gr-osmosdr && \
     cd gr-osmosdr && \
     mkdir build && \
     cd build && \
     cmake .. && \
-    make -j $(nproc) install
+    make -j $(nproc) install && \
+    ldconfig
 
 RUN mkdir /src/build
 WORKDIR /src/build
 
-RUN cmake .. && \
+RUN PYTHONPATH=/usr/local/lib/python3/dist-packages/:$PYTHONPATH cmake .. && \
     # The parallel build sometimes fails when the .grc_gnuradio
     # and .gnuradio directories do not exist
     mkdir $HOME/.grc_gnuradio/ $HOME/.gnuradio/ && \

tests/dockerfiles/Kali.docker

@@ -26,18 +26,20 @@ RUN git clone --branch maint-3.8 --recurse-submodules https://github.com/velichk
     mkdir build && \
     cd build && \
     cmake .. && \
-    make -j $(nproc) install
+    make -j $(nproc) install && \
+    ldconfig
 
 RUN git clone --branch maint-3.8 https://github.com/velichkov/gr-osmosdr && \
     cd gr-osmosdr && \
     mkdir build && \
     cd build && \
     cmake .. && \
-    make -j $(nproc) install
+    make -j $(nproc) install && \
+    ldconfig
 
 RUN mkdir /src/build
 WORKDIR /src/build
-RUN cmake .. && \
+RUN PYTHONPATH=/usr/local/lib/python3/dist-packages/:$PYTHONPATH cmake .. && \
     # The parallel build sometimes fails when the .grc_gnuradio
     # and .gnuradio directories do not exist
     mkdir $HOME/.grc_gnuradio/ $HOME/.gnuradio/ && \