Cannot find database driver: org.postgresql.Driver

Edit:

The problem was resolved by replacing
driver: org.postgresql.Driver with driver=org.postgresql.Driver in the liquibase.properties file.

Original Answer:

You have added the postgresql driver as a dependency of your webapp. But when maven plugins run, they have their own classpath, which is different to your webapp. So you need to include a dependency on the JDBC driver for the plugin itself (same applies to other plugins, e.g. jetty-maven-plugin):

<plugin>    <groupId>org.liquibase</groupId>    <artifactId>liquibase-maven-plugin</artifactId>    <version>2.0.5</version>    <configuration>        <propertyFileWillOverride>true</propertyFileWillOverride>        <propertyFile>src/main/resources/liquibase.properties</propertyFile>        <changeLogFile>src/main/resources/changelogs/changelog.xml</changeLogFile>    </configuration>    <executions>        <execution>            <!--  Another Error: plugin execution not covered by lifecycle configuration..-->            <!-- <phase>process-resources</phase> <goals> <goal>update</goal> </goals> -->        </execution>    </executions>    <dependencies>        <dependency>            <groupId>postgresql</groupId>            <artifactId>postgresql</artifactId>            <version>9.1-901-1.jdbc4</version>        </dependency>    </dependencies></plugin>

Following plugin configuration worked for me.

         <plugin>            <groupId>org.liquibase</groupId>            <artifactId>liquibase-maven-plugin</artifactId>            <version>3.5.0</version>            <configuration>            <propertyFile>src/main/resources/liquibase.properties</propertyFile>            </configuration>            <executions>                <execution>                    <goals>                        <goal>update</goal>                    </goals>                </execution>            </executions>        </plugin>